This patch is the result of running
run-clang-tidy -fix -header-filter=.* -checks='-*,modernize-use-equals-default' .

Code style changes have been done on top. The result of this change
leads to the following improvements:

1. Binary size reduction.
* For a -DBUILD_CONFIG=mysql_release build, the binary size is reduced by
  ~400kb.
* A raw -DCMAKE_BUILD_TYPE=Release reduces the binary size by ~1.4kb.

2. Compiler can better understand the intent of the code, thus it leads
   to more optimization possibilities. Additionally it enabled detecting
   unused variables that had an empty default constructor but not marked
   so explicitly.

   Particular change required following this patch in sql/opt_range.cc

   result_keys, an unused template class Bitmap now correctly issues
   unused variable warnings.

   Setting Bitmap template class constructor to default allows the compiler
   to identify that there are no side-effects when instantiating the class.
   Previously the compiler could not issue the warning as it assumed Bitmap
   class (being a template) would not be performing a NO-OP for its default
   constructor. This prevented the "unused variable warning".

- Added sql/mariadb.h file that should be included first by files in sql
  directory, if sql_plugin.h is not used (sql_plugin.h adds SHOW variables
  that must be done before my_global.h is included)
- Removed a lot of include my_global.h from include files
- Removed include's of some files that my_global.h automatically includes
- Removed duplicated include's of my_sys.h
- Replaced include my_config.h with my_global.h

Clean-up nolock.h: it doesn't serve any purpose anymore. Appropriate code moved
to x86-gcc.h and my_atomic.h.

If gcc sync bultins were detected, we want to make use of them independently of
__GNUC__ definition. E.g. XLC simulates those, but doesn't define __GNUC__.

HS/Spider: According to AIX manual alloca() returns char*, which cannot be
casted to any type with static_cast. Use explicit cast instead.

MDL: Removed namemangling pragma, which didn't let MariaDB build with XLC.

WSREP: _int64 seem to be conflicting name with XLC, replaced with _integer64.

CONNECT: RTLD_NOLOAD is GNU extention. Removed rather meaningless check if
library is loaded. Multiple dlopen()'s of the same library are permitted,
and it never gets closed anyway. Except for error, which was a bug: it may
close library, which can still be referenced by other subsystems.

InnoDB: __ppc_get_timebase() is GNU extention. Only use it when __GLIBC__ is
defined.

Based on contribution by flynn1973.

MDEV-9278 - Debian: the Lintian complains about "shlib-calls-exit" in ha_spider.so

Handlersocket handles errors in a way that it aborts program execution. In most
cases it is done via abort(). One exception was host/service resolution failure,
which was aborted with exit().

As a workaround replaced this exit() with abort() for symmetry with other error
handling.

stat structure (from <sys/stat.h>) is conditionally defined
to have different layout and size depending on the defined macros.
The correct macro is defined in my_config.h, which means it MUST be
included first (or, at least before <features.h> - so, practically,
before including any system headers).

Fixed some mtr test problems



dbug/tests.c:
  Fixed compiler warnings
mysql-test/r/handlersocket.result:
  Fixed that plugin_license is written
mysql-test/suite/innodb/t/innodb_bug60196.test:
  Force sorted results as it was sometimes different on windows
mysql-test/suite/rpl/t/rpl_heartbeat_basic.test:
  Prolong test as this failed on windows
mysql-test/t/handlersocket.test:
  Fixed that plugin_license is written
plugin/handler_socket/handlersocket/handlersocket.cpp:
  Use maria_declare_plugin
plugin/handler_socket/handlersocket/mysql_incl.hpp:
  Fixed compiler warning
plugin/handler_socket/libhsclient/auto_addrinfo.hpp:
  Fixed compiler warning
sql/handler.h:
  Fixed typo
sql/sql_plugin.cc:
  Fixed bug that caused plugin library name twice in error message
storage/maria/ma_checkpoint.c:
  Fixed compiler warning
storage/maria/ma_loghandler.c:
  Fixed compiler warning
unittest/mysys/base64-t.c:
  Fixed compiler warning
unittest/mysys/bitmap-t.c:
  Fixed compiler warning
unittest/mysys/my_malloc-t.c:
  Fixed compiler warning