PDF-comment.lyx: reset style and some fixes

- the example was designed to follow the style of the other LyX documentation files, e.g. not to insert options as one big TeX-code inset.
- fix some typos
- (I cannot save files with LyX 2.2 atm due to bug #9234)
Merge remote-tracking branch 'github/build-bot-master' into bleeding-edge-master
2014.11.02-00.00