ports/156747: multimedia/mplayer: fix 24-bits OSS + some improvements

[Zhihao Yuan]

Hi,

My final patches applies to mplayer and mencoder. After some
discussion, I think they are stable enough. I hope someone can take
this PR soon (before next upstream update, at least). Thanks so much.

http://www.freebsd.org/cgi/query-pr.cgi?pr=ports/156747

-- 
Zhihao Yuan
The best way to predict the future is to invent it.