Updated SDL's YUV support, many thanks to Adrien Descamps

New functions get and set the YUV colorspace conversion mode:
	SDL_SetYUVConversionMode()
	SDL_GetYUVConversionMode()
	SDL_GetYUVConversionModeForResolution()

SDL_ConvertPixels() converts between all supported RGB and YUV formats, with SSE acceleration for converting from planar YUV formats (YV12, NV12, etc) to common RGB/RGBA formats.

Added a new test program, testyuv, to verify correctness and speed of YUV conversion functionality.

src/dynapi/SDL_dynapi_overrides.h

@@ -660,3 +660,6 @@
 #define SDL_scalbnf SDL_scalbnf_REAL
 #define SDL_fmod SDL_fmod_REAL
 #define SDL_fmodf SDL_fmodf_REAL
+#define SDL_SetYUVConversionMode SDL_SetYUVConversionMode_REAL
+#define SDL_GetYUVConversionMode SDL_GetYUVConversionMode_REAL
+#define SDL_GetYUVConversionModeForResolution SDL_GetYUVConversionModeForResolution_REAL

src/dynapi/SDL_dynapi_procs.h

@@ -694,3 +694,6 @@ SDL_DYNAPI_PROC(float,SDL_powf,(float a, float b),(a,b),return)
 SDL_DYNAPI_PROC(float,SDL_scalbnf,(float a, int b),(a,b),return)
 SDL_DYNAPI_PROC(double,SDL_fmod,(double a, double b),(a,b),return)
 SDL_DYNAPI_PROC(float,SDL_fmodf,(float a, float b),(a,b),return)
+SDL_DYNAPI_PROC(void,SDL_SetYUVConversionMode,(SDL_YUV_CONVERSION_MODE a),(a),)
+SDL_DYNAPI_PROC(SDL_YUV_CONVERSION_MODE,SDL_GetYUVConversionMode,(void),(),return)
+SDL_DYNAPI_PROC(SDL_YUV_CONVERSION_MODE,SDL_GetYUVConversionModeForResolution,(int a, int b),(a,b),return)