Clean up and improve the parallel implementation code, mainly related to
scheduling of work to threads and handling of stop and errors.

Fix a lot of bugs in various corner cases that could lead to crashes or
corruption.

Fix that a single replication domain could easily grab all worker threads and
stall all other domains; now a configuration variable
--slave-domain-parallel-threads allows to limit the number of
workers.

Allow next event group to start as soon as previous group begins the commit
phase (as opposed to when it ends it); this allows multiple event groups on
the slave to participate in group commit, even when no other opportunities for
parallelism are available.

Various fixes:

 - Fix some races in the rpl.rpl_parallel test case.

 - Fix an old incorrect assertion in Log_event iocache read.

 - Fix repeated malloc/free of wait_for_commit and rpl_group_info objects.

 - Simplify wait_for_commit wakeup logic.

 - Fix one case in queue_for_group_commit() where killing one thread would
   fail to correctly signal the error to the next, causing loss of the
   transaction after slave restart.

 - Fix leaking of pthreads (and their allocated stack) due to missing
   PTHREAD_CREATE_DETACHED attribute.

 - Fix how one batch of group-committed transactions wait for the previous
   batch before starting to execute themselves. The old code had a very
   complex scheduling where the first transaction was handled differently,
   with subtle bugs in corner cases. Now each event group is always scheduled
   for a new worker (in a round-robin fashion amongst available workers).
   Keep a count of how many transactions have started to commit, and wait for
   that counter to reach the appropriate value.

 - Fix slave stop to wait for all workers to actually complete processing;
   before, the wait was for update of last_committed_sub_id, which happens a
   bit earlier, and could leave worker threads potentially accessing bits of
   the replication state that is no longer valid after slave stop.

 - Fix a couple of places where the test suite would kill a thread waiting
   inside enter_cond() in connection with debug_sync; debug_sync + kill can
   crash in rare cases due to a race with mysys_var_current_mutex in this
   case.

 - Fix some corner cases where we had enter_cond() but no exit_cond().

 - Fix that we could get failure in wait_for_prior_commit() but forget to flag
   the error with my_error().

 - Fix slave stop (both for normal stop and stop due to error). Now, at stop
   we pick a specific safe point (in terms of event groups executed) and make
   sure that all event groups before that point are executed to completion,
   and that no event group after start executing; this ensures a safe place to
   restart replication, even for non-transactional stuff/DDL. In error stop,
   make sure that all prior event groups are allowed to execute to completion,
   and that any later event groups that have started are rolled back, if
   possible. The old code could leave eg. T1 and T3 committed but T2 not, or
   it could even leave half a transaction not rolled back in some random
   worker, which would cause big problems when that worker was later reused
   after slave restart.

 - Fix the accounting of amount of events queued for one worker. Before, the
   amount was reduced immediately as soon as the events were dequeued (which
   happens all at once); this allowed twice the amount of events to be queued
   in memory for each single worker, which is not what users would expect.

 - Fix that an error set during execution of one event was sometimes not
   cleared before executing the next, causing problems with the error
   reporting.

 - Fix incorrect handling of thd->killed in worker threads.

- Make is_key_scan_ror() take into account the existence of extended keys.

- Change the default flag value to ON.
- Update the testcases to be run extended_keys=ON:
  = trivial test result updates
  = If extended_keys setting makes a difference for a testcase, run the testcase 
    with extended_keys=off. There were only a few such cases
- Update to vcol_select_innodb looks like a worse plan but it will be gone in 10.0.

update_used_tables for the the where condition to update cached
indicators of constant subexpressions. It should be done before further
possible simplification of the where condition.

This change caused simplification of the executed where conditions 
in many test cases.

In ::position() federated needs to know an element before the
current ("data_cursor") in the single-linked list. Replace list
traversal for every ::position() call (which is O(n^2)) with remembering
the current element before it's advanced by mysql_fetch_row().

storage/federatedx/federatedx_io_mysql.cc:
  mdev:5698

Use 20-year ssl certificates for mysql-test from RedHat patch

On fedora:
1. provide/obsoleve mariadb-* packages
2. MariaDB-common conflicts with mariadb-libs (on filesystem level),
   but does not provide or obsolete it.

* readability fixes
* CPackRPM wrapper to fix property leakage between components (cmake bug 13248)

might end up having the same query id

An attempt to introduce libmysqlclient.so symbol versioning that is
compatible both with Debian and Fedora all versions: put all symbols into
libmysqlclient_18 version node (as on Debian), but also put aliases of
old symbols into libmysqlclient_16 version node (as on Fedora).

Also use a linker script to create aliases of exported symbols, not
rpm_support.cc source file.

MDEV-4556 Server crashes in SEL_ARG::rb_insert with index_merge+index_merge_sort_union, FORCE INDEX
- merge_same_index_scans() may put the same SEL_ARG tree in multiple result plans.
  make it call incr_refs() on the SEL_ARG trees that it does key_or() on, because 
  key_or(sel_arg_tree_1, sel_arg_tree_2) call may invalidate SEL_ARG trees pointed 
  by sel_arg_tree_1 and sel_arg_tree_2.
    

In function ‘void* memset(void*, int, size_t)’,
    inlined from ‘void Lifo_buffer::set_buffer_space(uchar*, uchar*)’ at sql_lifo_buffer.h:70:5,
    inlined from ‘int DsMrr_impl::dsmrr_init(handler*, RANGE_SEQ_IF*, void*, uint, uint, HANDLER_BUFFER*)’ at multi_range_read.cc:895:62:
/usr/include/i386-linux-gnu/bits/string3.h:82:32: error: call to ‘__warn_memset_zero_len’ declared with attribute warning: memset used with constant zero length parameter; this could be due to transposed parameters [-Werror]

It was intentional that the buffer is set to zero length there.

(gdb) p dbug_print_table_row(table)
  $33 = "SUBQUERY2_t1(col_int_key,col_varchar_nokey)=(7,c)"

- Item_direct_view_ref didn't clear its pointer to item_equal in ::cleanup.
- Some Item_direct_view_ref objects have statement lifetime (i.e. they
  survive across multiple EXECUTE commands). Item_equal objects live only for
  the duration of one EXECUTE. This caused Item_direct_view_ref to have a stale pointer,
  which could cause all sorts of effects. (In this bug's testcase it was pointing to
  the wrong Item_equal, causing wrong query result)
- Fixed by doing what Item_field::cleanup() does - don't keep item_equal pointer value.
- There is no testcase because the only testcase I've got is highly fragile (e.g. the
  bug will not show up if @@datadir is of the wrong length).

Fixed so the MYSQL_TYPE_GEOMETRY is treated as BLOB.

The result is EMPTY for a buffer(line, -1), but we still
need one FALSE operation to be stored in the condition.
And we actually add it but forgot to alloc memory to store it.

Wait until the server starts accepting connections, not until the pid file appears

daemon plugin: join the thread to make sure it exits before the plugin is unloaded

It helps to interpret valgrind/safemalloc memory-related warnings that are
printed when a plugin is unloaded (and thus cannot resolve addresses automatically)

Handles the case of
sysctl net.ipv6.conf.all.disable_ipv6=1 net.ipv6.conf.default.disable_ipv6=1

don't include m_string. in my_valgrind.h

actually consumed it. With this patch evaluated query buffer is freed
along with query buffer.

The problem was uncovered by udf_debug_sync.test when it was run with
--embedded.

with Oracle's fix for Bug#17588348 by reverting Oracle's fix.

MDEV-5555: Incorrect index_merge on BTREE indices
- In ha_partition, make ordered index reads return rows in rowid order
  when index columns are the same.