Implement bare minimum for SDL_FlashWindow

src/dynapi/SDL_dynapi_overrides.h

@@ -811,3 +811,4 @@
 #define SDL_GetAudioDeviceSpec SDL_GetAudioDeviceSpec_REAL
 #define SDL_TLSCleanup SDL_TLSCleanup_REAL
 #define SDL_SetWindowAlwaysOnTop SDL_SetWindowAlwaysOnTop_REAL
+#define SDL_FlashWindow SDL_FlashWindow_REAL

src/dynapi/SDL_dynapi_procs.h

@@ -876,3 +876,4 @@ SDL_DYNAPI_PROC(int,SDL_AndroidShowToast,(const char *a, int b, int c, int d, in
 SDL_DYNAPI_PROC(int,SDL_GetAudioDeviceSpec,(int a, int b, SDL_AudioSpec *c),(a,b,c),return)
 SDL_DYNAPI_PROC(void,SDL_TLSCleanup,(void),(),)
 SDL_DYNAPI_PROC(void,SDL_SetWindowAlwaysOnTop,(SDL_Window *a, SDL_bool b),(a,b),)
+SDL_DYNAPI_PROC(int,SDL_FlashWindow,(SDL_Window *a, Uint32 b),(a, b),return)