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