Fixed bug 3744 - missing SDLCALL in several functions

Ozkan Sezer

The attached patch adds missing SDLCALL to several functions, so that
they properly match the headers as intended.

test/testmessage.c

@@ -25,7 +25,7 @@ quit(int rc)
     exit(rc);
 }
 
-static int
+static int SDLCALL
 button_messagebox(void *eventNumber)
 {
     const SDL_MessageBoxButtonData buttons[] = {