Don't modify the "YCbCr Matrix" header when dummy video is opened

Color matching to dummy video makes zero sense, and setting it to None
results in breakage when someone opens dummy video for an already
typeset script.

Closes #1690.
Update and modify Chinese translations.
Merge pull request #8 from computerfan/patch-1

Update Simplified Chinese translations
Fix codecvt errors on OS X

When launching Aegisub from Finder (but not via open), using the UTF-8
version of the locale breaks things for whatever reason, but fortunately
it's unneccesary as paths on OS X are always UTF-8 even if the locale
isn't.

Closes #1685.
Update Hungarian translation. Closes #1693.
Updated Traditional Chinese translation.
Merge pull request #9 from computerfan/patch-2

Update Traditional Chinese translation.
Build with all icon sizes enabled on Windows. Closes #1692.
Hide visual tools for commented lines
Delete unused button bitmaps
Make respack less dumb
Update to ICU 52.1
Bump ffmpeg version
Build libass without iconv support

We only ever feed UTF-8 to it, and it doesn't check whether the input is
UTF-8 before converting.
Bump libass version