Fixed subtitles on black bands not being cleared (appear overlapped) on Sony Bravia EX TVs when using Mencoder (thanks, master-nevi!)

From https://github.com/master-nevi/UniversalMediaServer/commit/7a67d3a31ef8247fc9d3c58e310ffc942b55190f
Merge branch 'master' of github.com:UniversalMediaServer/UniversalMediaServer