Give the buffer screen a high zposition instead of the widget

This allows the screen itself is be on top so you also see the buffering
status when e.g. the 2nd infobar is visiable.
PangaSubtitles: Arrange that subtitles can be displayed Italic or Bold

And herefore remove alternative colloring as previously Italic was displayed as yellow
Still it does not feature everything that is possible in srt files as only whole lines
could be displayed in Italic and Bold and the font switch could not be made on a segment
of a line, but most subtitles do not have that.
Subtitle.xml: Scale the new subtitlefont as it looks larger than the old
eSubtitle: Solve go back to yellow for underscore

For underscore we do not have a sapertate skin. But it is rarely used in subs
so it was still displayed as green. No I changed it to cyan and when returened
to yellow instead of always white.
Merge branch 'master' of git://git.code.sf.net/p/openpli/enigma2