Fix problem with warnings of new compilers.

libmariadb @ c6403c4c

-Subproject commit 544b6f1d12f0e5b2a141129075ff2d64feb0e4c9
+Subproject commit c6403c4c847d94ed6b40d3fd128e729271867e75

sql-common/client_plugin.c

@@ -28,10 +28,8 @@
   There is no reference counting and no unloading either.
 */
 
-#if _MSC_VER
 /* Silence warnings about variable 'unused' being used. */
 #define FORCE_INIT_OF_VARS 1
-#endif
 
 #include <my_global.h>
 #include "mysql.h"