Added SDL_GameControllerMappingForDeviceIndex() to get the mapping for a controller before it's opened

src/dynapi/SDL_dynapi_overrides.h

@@ -669,3 +669,4 @@
 #define SDL_WinRTGetDeviceFamily SDL_WinRTGetDeviceFamily_REAL
 #define SDL_log10 SDL_log10_REAL
 #define SDL_log10f SDL_log10f_REAL
+#define SDL_GameControllerMappingForDeviceIndex SDL_GameControllerMappingForDeviceIndex_REAL

src/dynapi/SDL_dynapi_procs.h

@@ -707,3 +707,4 @@ SDL_DYNAPI_PROC(SDL_bool,SDL_IsAndroidTV,(void),(),return)
 #endif
 SDL_DYNAPI_PROC(double,SDL_log10,(double a),(a),return)
 SDL_DYNAPI_PROC(float,SDL_log10f,(float a),(a),return)
+SDL_DYNAPI_PROC(char*,SDL_GameControllerMappingForDeviceIndex,(int a),(a),return)