[FFmpeg-cvslog] doc: fix various typos and grammar errors

ffmpeg | branch: release/3.1 | Moritz Barsnick | Sun Oct 9 20:51:57 2016 +0200| [6109c10b81d6bc484996e3407046302d3a537575] | committer: Michael Niedermayer doc: fix various typos and grammar errors Signed-off-by: Moritz Barsnick Signed-off-by: Michael Niedermayer (cherry picked from commit

[FFmpeg-cvslog] doc: fix various typos and grammar errors

ffmpeg | branch: master | Moritz Barsnick | Sun Oct 9 20:51:57 2016 +0200| [99d68d462fbd777cfd3fe055d4181a6f7c03fac7] | committer: Michael Niedermayer doc: fix various typos and grammar errors Signed-off-by: Moritz Barsnick Signed-off-by: Michael Niedermayer > http://git.videolan.org/gitwe