Add support for the Nokia N-Gage (#5597)

* Add initial support for the Nokia N-Gage

* N-Gage: disable clipping for the time being, issue needs to be resolved later

* Move va_copy definition to SDL_internal.h

* Move stdlib.h include to SDL_config_ngage.h, much cleaner this way

* Remove redundant include, add HAVE_STDLIB_H

* Revert "N-Gage: disable clipping for the time being, issue needs to be resolved later"

This reverts commit 4f5f0fc36c.

* N-Gage: fix clipping issue by providing proper math functions

src/SDL.c

@@ -567,6 +567,8 @@ SDL_GetPlatform(void)
     return "PlayStation Portable";
 #elif __VITA__
     return "PlayStation Vita";
+#elif __NGAGE__
+    return "Nokia N-Gage";
 #else
     return "Unknown (see SDL_platform.h)";
 #endif