ASS/SSA subtitles: Fix a possible infinite loop during parsing.

The wrong loop index was incremented after a typo in 21298a3d04befa61f59e0f063a019f748f54af55.

This commit fixes #4173.
Shaders option page: the buttons' icons were missing on Windows XP.

This commit fixes #4163.
Update translations from Transifex:

 - Basque
 - Italian
 - Japanese
 - Portuguese (Brazil)
 - Slovak
 - Spanish
 - Swedish
Add a Tatar translation.

The composition of the translation team can be found on Transifex: https://www.transifex.com/projects/p/mpc-hc/language/tt/members/.