Fixed bug 4277 - warnings patch

Sylvain

Patch a few warnings when using:
-Wmissing-prototypes -Wdocumentation -Wdocumentation-unknown-command

They are automatically enabled with -Wall

src/cpuinfo/SDL_cpuinfo.c

@@ -22,6 +22,7 @@
 #include "SDL_config.h"
 #else
 #include "../SDL_internal.h"
+#include "SDL_simd.h"
 #endif
 
 #if defined(__WIN32__)