Test galera_3nodes.galera_pc_weight started to fail because it
expects to use wait_until_connected_again while remaining in
non-primary view. Hopefully this is the only test which makes
this assumption, and fortunately those wait_until_connected_again
seem unnecessary, so this patch removes them.

Remove clause on `thd->variables.wsrep_on` in the following code:

if (WSREP(thd))
{
...
        if (thd->variables.wsrep_on &&
            ...

In the above snippet, `WSREP(thd)` already ensures thd->variables.wsrep_on

wait_until_connected_again issues 'SHOW STATUS' query repeatedly
until mysqld replies without errors.
However, SHOW STATUS is treated specially by wsrep in that it is
allowed to proceed even if wsrep is not yet in ready state. As a
consequence, after returning from wait_until_connected_again,
wsrep may not be ready yet and subsequent queries may fail with
error "1047 WSREP has not yet prepared node for application use".
To avoid those errors, the patch includes wait_wsrep_ready.inc at
the end of the wait_until_connected_again.

MDEV-13549 Fix and re-enable MTR test galera.galera_gtid_slave

MDEV-13549 Fix and re-enable MTR test galera.galera_as_master

This patch makes two changes:

* It replaces `--sleep 1` with appropriate wait_conditions, and
  removes another `--sleep 1` which is no longer necessary, after
  MDEV-14144 has been fixed.

* It moves the `RESET MASTER` from node_1 at the very end, when it
  it sure that the other nodes have applied the the final cleanup
  `DROP TABLE t1,t2.`
  This solves the problem with the `DROP TABLE` not being replicated
  to the asynchronous slaves, which would make the test fail with:
  `Timeout in wait_condition.inc for SELECT COUNT(*) = 0 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 't1';`

MDEV-13549 Fix and re-enable test galera.galera_suspend_slave

Was failing due to missing RESET MASTER

Test galera_suspend_slave checks that after suspending a galera
node, like this:
```
--perl
        my $pid_filename = $ENV{'NODE_2_PIDFILE'};
        my $mysqld_pid = `cat $pid_filename`;
        chomp($mysqld_pid);
        system("kill -SIGSTOP $mysqld_pid");
        exit(0);
EOF
```

the remaining one node cluster is no longer able to successfully
INSERT new rows:
```
--error ER_UNKNOWN_COM_ERROR,ER_LOCK_WAIT_TIMEOUT,ER_LOCK_DEADLOCK,ER_ERROR_DURING_COMMIT
INSERT INTO t1 VALUES (1);
```

On rare occasions when the system is overloaded, it appears that
suspending the process with ```system("kill -SIGSTOP $mysqld_pid")```
takes some time, enough for the subsequent INSERT to succeed. In which
case the test fails because it rightly expects the INSERT to fail.

To fix the problem, the patch makes sure that the cluster has shrinked
to one node, before trying to INSERT the new value.

MDEV--15609 engines/funcs.crash_manytables_number crashes with error 24
           (too many open files)
MDEV-10286  Adjustment of table_open_cache according to system limits
            does not work when open-files-limit option is provided

Fixed by adjusting tc_size downwards if there is not enough file
descriptors to use.

Other changes:
- Ensure that there is 30 (was 10) extra file descriptors for other usage
- Decrease TABLE_OPEN_CACHE_MIN to 200 as it's better to have a smaller
  table cache than getting error 24
- Increase minimum of max_connections and table_open_cache from 1 to 10
  as 1 is not usable for any real application, only for testing.

and remove redundant have_innodb.inc, it's included in
galera_cluster.inc anyway.

and remove redundant have_innodb.inc, it's included in
galera_cluster.inc anyway.

extra/mariabackup/ds_buffer.c:145:9: warning: pointer targets in assignment differ in signedness [-Wpointer-sign]

information can be obtained.

plugin only enabled for Linux, as it fails building on BSD/MacOSX.
disks.test fixed.

information can be obtained.

disks.test moved to plugin's directory.

Changed "local" datasink logic to detect page compressed Innodb tables.

Whenever such table is detected, holes in the copied files are created by
skipping over binary zeros at the end of each compressed page.

             time and don't let server shut down

Queries from I_S in "Filling schema table" state didn't check killed
flag. For large tables this phase may take a while to complete.

Fixed by adding thd->killed flag check for each processed row.

galera SST tests have a debug part, but we don't want to limit them
to fulltest2 builder. So, add support for test files that
have a debug part:

* add maybe_debug.inc and maybe_debug.combinations
* 'debug' combination is run when debug is available
* 'release' combination is run otherwise
* test wraps debug parts in if($with_debug) { ... }
* and creates ,debug.rdiff for debug results

create galera.galera_sst_mariabackup

* make galera.galera_sst_xtrabackup* not big
* auto-select between socat and nc, whatever available
* auto-skip xtrabackup tests if no xtrabackup or neither socat nor nc

make galera.galera_sst_rsync not big

fix galera.galera_sst_mysqldump test to work:
* must connect to 127.0.0.1, where mysqld is listening
* disable wsrep_sync_wait in wsrep_sst_mysqldump, otherwise
  sst can deadlock
* allow 127.0.0.1 for bind_address and wsrep_sst_receive_address.
  (it's useful in tests, or when two nodes are on the same box,
  or when nodes are on different boxes, but the connection is
  tunelled, or whatever. Don't judge user's setup). MDEV-14070
* don't wait for client connections to die when doing
  mysqldump sst. they'll die in a due time, and if needed mysql
  will wait on locks until they do. MDEV-14069

Also don't mark it big, to make sure it's sufficiently tested

wsrep_sst_auth_init() is always invoked with value==wsrep_sst_auth.
Old code was leaking value, because it was never freed.

in particular, don't call server_version_string() unnecessary,
because it runs 'SELECT @@version_comment' and this might block
under certain galera settings (wsrep_sync_wait).

Backport from 10.2: 4c2c057d and f7090df7

It doesn't make sense to allow selects from I_S but disallow selects
that don't use any tables at all, because any (disallowed) select that
doesn't use tables can be made allowed by adding
"FROM I_S.COLLATIONS LIMIT 1" to the end.

And it break mysql-test rather badly, even check-testcase.test
fails on its first `SELECT '$tmp' = 'No such row'`

This reverts 9a896148, c5dd2abf, and 33028f7c:
Refs: MW-245 - changed logic so that in non primary node it is possible to do SET + SHOW + SELECT from information and pfs schema, when dirty reads are not enabled - however, non table selects are not allowed (e.g. SELECT 1)
Refs MW-245 - logic was wrong in detecting if queries are allowed in non primary node. it allowed select with no table list to execute even if dirty reads was not specified
Refs: MW-245 - Adjust tests to account for the new behavior.

update README, use maria_declare_plugin(), specify the author.

The 'debug' option implemented for the pam_user_map.so.

- Mariabackup supports starting undo tablespace id which is greater
than 1.

Conversion of a subquery to a semi-join is blocked when we have an
IN subquery predicate in the on_expr of an outer join. Currently this
scenario is handled but the cases when an IN subquery predicate is wrapped
inside a Item_in_optimizer item then this blocking is not done.