Fix: Some subtitles could have been missing.

Depending on how the subtitle entries overlapped in time, some segments were forgotten when creating them on the fly which led to incomplete rendering.

This regression in ef0327fa92b6938f5ef70dea49fe2ecbbd86757b was made visible by fa670bfc0b1d4d620bfc0388e9fd41b6275e8d4f.
Subtitle renderer: Fix the Gaussian blur SSE2 filter for small subpicture.

The blur filter was applied twice on some part of the subpicture when the size was too small to use SSE2.

This commit fixes #3981.
Update translations from Transifex:

 - Armenian
 - Basque
 - Chinese (simplified)
 - French
 - German
 - Japanese
 - Portuguese (Brazil)
 - Swedish
 - Turkish
 - Ukrainian