Use consistent identifiers for the various platforms we support.

Make sure every source file includes SDL_config.h, so the proper system
headers are chosen.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%401406

include/SDL_cpuinfo.h

@@ -23,11 +23,11 @@
 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 /* CPU feature detection for SDL                                       */
 
-#include "SDL_stdinc.h"
-
 #ifndef _SDL_cpuinfo_h
 #define _SDL_cpuinfo_h
 
+#include "SDL_stdinc.h"
+
 #include "begin_code.h"
 /* Set up for C function definitions, even when using C++ */
 #ifdef __cplusplus