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

include/SDL_platform.h

@@ -65,6 +65,10 @@
 #undef __LINUX__ /* do we need to do this? */
 #define __ANDROID__ 1
 #endif
+#if defined(__NGAGE__)
+#undef __NGAGE__
+#define __NGAGE__ 1
+#endif
 
 #if defined(__APPLE__)
 /* lets us know what version of Mac OS X we're compiling on */