stdlib: added SDL_utf8strlen().

src/dynapi/SDL_dynapi_overrides.h

@@ -624,3 +624,4 @@
 #define SDL_MemoryBarrierReleaseFunction SDL_MemoryBarrierReleaseFunction_REAL
 #define SDL_MemoryBarrierAcquireFunction SDL_MemoryBarrierAcquireFunction_REAL
 #define SDL_JoystickGetDeviceInstanceID SDL_JoystickGetDeviceInstanceID_REAL
+#define SDL_utf8strlen SDL_utf8strlen_REAL

src/dynapi/SDL_dynapi_procs.h

@@ -656,3 +656,4 @@ SDL_DYNAPI_PROC(SDL_JoystickType,SDL_JoystickGetType,(SDL_Joystick *a),(a),retur
 SDL_DYNAPI_PROC(void,SDL_MemoryBarrierReleaseFunction,(void),(),)
 SDL_DYNAPI_PROC(void,SDL_MemoryBarrierAcquireFunction,(void),(),)
 SDL_DYNAPI_PROC(SDL_JoystickID,SDL_JoystickGetDeviceInstanceID,(int a),(a),return)
+SDL_DYNAPI_PROC(size_t,SDL_utf8strlen,(const char *a),(a),return)