Backport of "fix multiple unused-but-set warnings" into 1.20
Backport of !2046 (merged) "fix multiple unused-but-set warnings".
Commits:
- 5d76ddb4 osxcoreaudio: fix unused-but-set warning
- 6c49f8d3 mpeg: fix unused-but-set warning
- 6f95f726 mpegts: don't shadow res variable
- fc28db57 resindvd: silence unused-but-set warning
- f65b61fd speed: fix unused-but-set warning
- 651cd8e0 avfassetsrc: fix unused-but-set warning
- edd9ec04 avsamplevideosink: remove unused variable
- 49e45252 vtdec: remove unused variable
- b8f83c9d applemedia/iosgl: remove unused variable
- 3ffbb665 applemedia/corevideobuffer: remove unused variable
- b8a5e7a4 applemeida/texturecache: remove unused variable
- 67e364b3 rtsp-stream: remove unused variable:
- 8b82463b validate/media-info: silence unsed variable warning