Fix compilation failure on OSX due to missing include.

Fixes #1449
Extended icon theming options.

* New toolbar icon for self comment changes: self_comment.svg
* Different state icons for filter.svg (on/off)
* Added separate icon for priority_speaker: priority_speaker.svg
* Added copies of old icons for the new names so our
  base theme doesn't break.
Transifex translation update
Mode: default
Minimum percent translated: 0
Matched 31 languages
Transifex translation update
Mode: default
Minimum percent translated: 0
Matched 31 languages