Add some helper functions to check if a string matches an ISO 639 code or language.
Play > Subtitles menu: Improve the external subtitles naming.

Show the subtitle filename and detect the language whenever possible.
player.html: remove width completely.

It's handled in JS.
Initialize variables in the constructor.
Enable per-monitor DPI-aware on Windows 8.1.

Fixes #3356.
Add a Doxyfile to generate source doc.

WIP
Use DEBUG_NEW instead of new.
temp
Run astyle.