SubtitleInputPin: Handle samples without time.

This commit fixes DVB subtitles for live broadcast. We discard samples
without time for text subtitles since they make no sense there.
Updated LAV Filters to 0.63-5-7ffa765 (custom build based on stable version 0.63.0).
Update translations from Transifex:

 - Arabic
 - Basque
 - Chinese (Simplified)
 - Croatian
 - Czech
 - French
 - Galician
 - German
 - Greek
 - Japanese
 - Malay
 - Polish
 - Portuguese (Brazil)
 - Slovenian
 - Spanish
 - Swedish
 - Thai
 - Turkish
 - Vietnamese
Fix a preposition mistake in the English translation.
Changelog.txt: Document a bug fixed by a previous LAV Filters update.

a8d924b5b0d3a9352d4dc32361569c44baf61103 solved some stuttering issue with (m2)ts files (fixes #3608).
Update files for 1.7.7.