PGS Subtitles: Restore some locks that went missing during ffd5478189f7b27b0ccb7b4fff7307418ce77e98.

Some subtitles could be missing and generally some strange behaviors could occur.

Refs: #3691.
MainFrame: cosmetics

[](){} confused astyle here.
[]{} does not.
MainFrame: adjust auto-zoom logic

When video size changes during playback, reposition the window only
if "auto-zoom" AND "limit window proportions" options are enabled.

Refs #3704
MainFrame: fix aero-snap misdetection

Refs #4284
MainFrame: don't reset position when aero-snapped
MainFrame: don't access class as memory chunk
MainFrame: adjust auto-zoom logic yet more

We auto-zoom when we loose the video during playback.
So it makes sense to auto-zoom when we regain it too.
StatusBar: flickerless paint
InfoBar: fix aggressive relayout

Better performance. Fixes some visual glitches.
MainFrame: don't exit d3dfs in OnFilePostOpenmedia
Update Changelog.txt