Consider a query with subquery in form t.key=(select ...). Suppose, the
parent query uses this equality for ref access.
It will attempt to evaluate the subquery in get_best_combination(),
right before the join->join_tab[...] array is filled.  The problem was
that subquery optimization will attempt to look at parent's join->join_tab
to check how many times subquery will be executed (and crash).

Fixed by not doing that when the subquery is constant (non-constant
subqueries are only be evaluated during join execution, so they are not
affected)

cherry-pick f1daf9ce from 10.0 branch
-------------------------------------

Fix build failures caused by new C runtime library
- isnan, snprintf, struct timespec are now defined, attempt to
redefine them leads
- P_tmpdir, tzname are no more defined
-  lfind() and lsearch() in lf_hash.c had to be renamed,  declaration
conflicts with some C runtime functions with the same name declared in
a header included by stdlib.h

 Also fix couple of annoying warnings :
- remove #define NOMINMAX from config.h to avoid "redefined" compiler
warnings(NOMINMAX is already in compile flags)

- disable incremental linker in Debug as well (feature not used much
and compiler crashes often)

Also simplify package building with Wix, require Wix 3.9 or later
(VS2015 is not compatible with old Wix 3.5/3.6)

fix dynstr_append_os_quoted() to escape single quotes correctly
for a POSIX shell

and a trivial cleanup to avoid manually-specified lengths

Fixed adding derived tables items to outer one.

mysqlcheck tool can be used even if opt_systables_only is true
(to upgrade views from mysql - that overrides opt_systables_only)

MDEV-9314 fatal build error: viosslfactories.c:58:5: error: dereferencing pointer to incomplete type ‘DH {aka struct dh_st}

fixes for openssl that was built with -DOPENSSL_NO_DEPRECATED

MDEV-9433: Add va_end to sql/rpl_reporting.cc to make cppcheck happy

MDEV-7827: Assertion `!table || (!table->read_set || bitmap_is_set(table->read_set, field_index))' failed in Field_long::val_str on EXPLAIN EXTENDED

(Solution by Sergei Petrunia)
It appeared that semijoin conditions was not iterated when we were updating used tables. So now they do.

added lost virtual fields update call

MDEV-9471: Server crashes or returns an error while trying to alter partitioning on a table moved from Windows to Linux

At alter table when server renames the table to temporal name,
old name uses normal partioned table naming rules. However,
if tables are created on Windows and then transfered to Linux
and lower-case-table-names=1 we should modify the old name
on rename to lower case to be able to find it from the
InnoDB dictionary.

if mysqld runs as service

The bug is caused by the attempt to write to filedescriptor 2
(STDERR_FILENO), however in case of a service stderr has different fd
(debugging shows fileno(stderr) is 4 after freopen, and -1 before it)

Fixed definition of STDERR_FILENO for Windows to be fileno(stderr).

The check for UCONTEXT in cmake was somehow become broken, disabling the
fallback to ucontext. This caused the non-blocking client API to not be
available for non-x86 platforms, on which no hand-crafted assembler
implementation of my_context is available.

overrun that caused some test to fail.

Fixed by ensuring we don't overwrite "server_version"

        fixing Windows crash.

   updata thread_pool_server_audit test result.

    MariaDB 5.5 built in debug gets unhappy with mutexes.
    Although everything is correct, some DBUG_ASSERT can happen.
    So this patch keeps safe_mutex silent.

        The audit API was seriously changed in MySQL 5.7.
        so we had to adapt the plugin's code to that.

If GCC or CLang compile with link time optimization (-flto),
they throw an error during link , when lto sees a
function (e.g mysql_real_connect) is redeclared as "external void *"
in libmysql_exports.cc

The fix disables -flto for generated libmysql_exports.cc

Fix process  handle leak in buildbot. GenerateConsoleCtrlEvent sent to non-existing process will add a process handle to this non-existing process to console host process conhost.exe

as it's needed for Cassandra in 10.0.

MDEV-9249 MariaDB un-buildable on linux64: fails @ "error: ‘ERR_remove_state’ was not declared in this scope" when linking against OpenSSL 1.0.2e

ERR_remove_state is deprecated, use ERR_remove_thread_state
if possible

A string definition is inconsistent and thus causes a compilation error.
Signed-off-by: Vicențiu Ciorbaru <vicentiu@mariadb.org>

Fixed compile warning related to if statement always being true. The if
statement can not be false, as the address of a member field is always
true.

Removed unused functions from tokudb_dump.cc.

This patch fixes another compilation error caused by specifying
attribute nonnull for all the parameters of the copyout function. This
is incorrect as the function actually gets called with null parameters
indirectly and thus only the output parameter should be nonnull.

This patch fixes one compilation error related to __db_lsn struct. The
struct can not be defined as empty according to the main C standard.
In C++, this is handled by forcing a size of 1. To eliminate the error
we add a dummy char field of size 1. This has no effect on the C++
compiled code, but also removes the compiler error.

MDEV-7655 SHOW CREATE TABLE returns invalid DDL when using virtual columns along with a table collation

that was mistakenly merged from mysql-5.5.47

(introduces valgrind failures in main.sp, because Field_varstring
columns are created as FIELD_NORMAL and that causes aria to
read bytes between the actual value length and field max length)

that was mistakenly merged from mysql-5.5.47

while according to Storage Engine API column names should be compared
case insensitively. This can cause FRM and InnoDB data dictionary to
go out of sync.

In fact it was error in decimal library (incorrect processing of buffer overflow) invisible from other server parts because of buffer allocation and precision tests.