glapi: export glapi_destroy_multithread when building shared-glapi on windows

Which will allow meson to build a shared glapi build with mingw.

v2: - Add symbol to symbol check test

Reviewed-by: Eric Anholt <eric@anholt.net> (v1)
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>

src/mapi/glapi/glapi.h

@@ -114,7 +114,7 @@ _GLAPI_EXPORT extern void *_glapi_Context;
 #endif /* defined (USE_ELF_TLS) */
 
 
-void
+_GLAPI_EXPORT void
 _glapi_destroy_multithread(void);
 
 

src/mapi/shared-glapi/glapi-symbols.txt

@@ -2,6 +2,7 @@ _glapi_Context
 _glapi_Dispatch
 _glapi_add_dispatch
 _glapi_check_multithread
+_glapi_destroy_multithread
 _glapi_get_context
 _glapi_get_dispatch
 _glapi_get_dispatch_table_size