Fixed bug 4987 - Can't build on MinGW a recent state: conflicting types

Vitaly Novichkov

Recent attempt to build a recent HG state of SDL2 via AppVeyor gives the failure:

https://ci.appveyor.com/project/Wohlstand/sdl-mixer-x/builds/30821858/job/359gqvypi2f18nok

```
C:\projects\sdl-mixer-x\build-MinGW-w32-MinSizeRel-Win32-VB6-Binding\external\AudioCodecs\src\AudioCodecs-build\external\SDL2\src\SDL2HG\src\dynapi\SDL_dynapi_procs.h:56:29: error: conflicting types for 'SDL_CreateThread'
 SDL_DYNAPI_PROC(SDL_Thread*,SDL_CreateThread,(SDL_ThreadFunction a, const char *b, void *c),(a,b,c),return)

src/dynapi/SDL_dynapi_procs.h

@@ -48,7 +48,7 @@ SDL_DYNAPI_PROC(int,SDL_snprintf,(SDL_OUT_Z_CAP(b) char *a, size_t b, SDL_PRINTF
 #undef SDL_CreateThread
 #endif
 
-#if defined(__WIN32__) && !defined(HAVE_LIBC)
+#if defined(__WIN32__)
 SDL_DYNAPI_PROC(SDL_Thread*,SDL_CreateThread,(SDL_ThreadFunction a, const char *b, void *c, pfnSDL_CurrentBeginThread d, pfnSDL_CurrentEndThread e),(a,b,c,d,e),return)
 #elif defined(__OS2__)
 SDL_DYNAPI_PROC(SDL_Thread*,SDL_CreateThread,(SDL_ThreadFunction a, const char *b, void *c, pfnSDL_CurrentBeginThread d, pfnSDL_CurrentEndThread e),(a,b,c,d,e),return)