Fix bug 4746 - introduce SDL_zeroa macro.

include/SDL_stdinc.h

@@ -415,6 +415,7 @@ extern DECLSPEC void *SDLCALL SDL_memset(SDL_OUT_BYTECAP(len) void *dst, int c,
 
 #define SDL_zero(x) SDL_memset(&(x), 0, sizeof((x)))
 #define SDL_zerop(x) SDL_memset((x), 0, sizeof(*(x)))
+#define SDL_zeroa(x) SDL_memset((x), 0, sizeof((x)))
 
 /* Note that memset() is a byte assignment and this is a 32-bit assignment, so they're not directly equivalent. */
 SDL_FORCE_INLINE void SDL_memset4(void *dst, Uint32 val, size_t dwords)