Configure dynamically generates SDL_config.h

I'm still wrestling with autoheader, but this should work for now...
Fixed lots of build problems with C library support disabled

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%401345

src/audio/dma/SDL_dmaaudio.c

@@ -23,6 +23,7 @@
 /* Allow access to a raw mixing buffer */
 
 #include <stdio.h>
+#include <string.h>	/* For strerror() */
 #include <errno.h>
 #include <unistd.h>
 #include <fcntl.h>