Enusure that my_global.h is included first

- 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

sql/mysql_upgrade_service.cc

@@ -20,8 +20,8 @@
 */
 
 #define DONT_DEFINE_VOID
+#include "mariadb.h"
 #include <process.h>
-#include <my_global.h>
 #include <my_getopt.h>
 #include <my_sys.h>
 #include <m_string.h>
@@ -519,4 +519,4 @@ int main(int argc, char **argv)
     CloseHandle(logfile_handle);
   my_end(0);
   exit(0);
-}
+}