Android doesn't have libunwind.h in API 16

include/SDL_config_android.h

@@ -46,7 +46,6 @@
 #define HAVE_STDIO_H    1
 #define HAVE_STRING_H   1
 #define HAVE_SYS_TYPES_H    1
-#define HAVE_LIBUNWIND_H    1
 
 /* C library functions */
 #define HAVE_MALLOC 1