Fixed bug 2376 - no SDL_HasAVX

Haneef Mubarak

AVX is the successor to SSE* and is fairly widely available. As such, it really ought to be detectable.

This functionality ought to be trivial to implement, and not having it means being forced to write an ugly workaround to check for AVX (so that normal SSE can be used if AVX is not available).

Here is an example on detecting AVX from SO (it actually shows ways to cehck for all of teh fancy instructions):

http://stackoverflow.com/questions/6121792/how-to-check-if-a-cpu-supports-the-sse3-instruction-set

src/dynapi/SDL_dynapi_overrides.h

@@ -571,3 +571,4 @@
 #define SDL_vsscanf SDL_vsscanf_REAL
 #define SDL_GameControllerAddMappingsFromRW SDL_GameControllerAddMappingsFromRW_REAL
 #define SDL_GL_ResetAttributes SDL_GL_ResetAttributes_REAL
+#define SDL_HasAVX SDL_HasAVX_REAL

src/dynapi/SDL_dynapi_procs.h

@@ -600,3 +600,4 @@ SDL_DYNAPI_PROC(void,SDL_GL_DeleteContext,(SDL_GLContext a),(a),)
 SDL_DYNAPI_PROC(int,SDL_vsscanf,(const char *a, const char *b, va_list c),(a,b,c),return)
 SDL_DYNAPI_PROC(int,SDL_GameControllerAddMappingsFromRW,(SDL_RWops *a, int b),(a,b),return)
 SDL_DYNAPI_PROC(void,SDL_GL_ResetAttributes,(void),(),)
+SDL_DYNAPI_PROC(SDL_bool,SDL_HasAVX,(void),(),return)