Merge commit '608e8d8dd754199b657b439f9e722e0b45f84461' into release/2.4

* commit '608e8d8dd754199b657b439f9e722e0b45f84461':
  vf_drawtext: Do not leak the mmapped textfile

Conflicts:
	libavfilter/vf_drawtext.c

See: 6956b048d8
Merged-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/vf_drawtext.c

@@ -485,7 +485,7 @@ static int load_textfile(AVFilterContext *ctx)
         return err;
     }
 
-    if (!(tmp = av_realloc(s->text, textbuf_size + 1))) {
+    if (textbuf_size > SIZE_MAX - 1 || !(tmp = av_realloc(s->text, textbuf_size + 1))) {
         av_file_unmap(textbuf, textbuf_size);
         return AVERROR(ENOMEM);
     }