audio: SDL_ResampleCVT() should use memmove instead of memcpy.

This copy can overlap.

Fixes Bugzilla #3849.

src/audio/SDL_audiocvt.c

@@ -732,7 +732,7 @@ SDL_ResampleCVT(SDL_AudioCVT *cvt, const int chans, const SDL_AudioFormat format
 
     SDL_free(padding);
 
-    SDL_memcpy(cvt->buf, dst, cvt->len_cvt);  /* !!! FIXME: remove this if we can get the resampler to work in-place again. */
+    SDL_memmove(cvt->buf, dst, cvt->len_cvt);  /* !!! FIXME: remove this if we can get the resampler to work in-place again. */
 
     if (cvt->filters[++cvt->filter_index]) {
         cvt->filters[cvt->filter_index](cvt, format);