ffmpeg 2.1.1

2.1.1 was released on 2013-11-20. It is the latest stable FFmpeg
release from the 2.1 release branch, which was cut from master on
2013-10-28.

Despite being stable, this is only a devel option to ensure
compatibility with other formulae that do not build with ffmpeg 2.x.

Closes #24727.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>