Subtitle renderer: Fix parsing of some animated transform tags.

\t(<t1>,<t2>,<accel>,<style modifiers>) tags were wrongly parsed because of a typo: <t1> was used as <accel>.
Subtitle renderer: Fix a crash on malformed animated transforms.

\t tags with no parameters led to a crash.

This commit fixes #4013.
Update translations from Transifex:

 - Galician
 - Japanese
 - Romanian
 - Vietnamese
Language menu: Ensure "Language" always appears in English in menu entry.

If "Language" doesn't appear in the translated string, "(Language)" will be appended automatically.
Language menu: Use submenus to group language names starting with the same character.
Update translations from Transifex:

 - Greek.