Update TODO.
Add Czech translation.
Restore drop-down arrows on undo and redo toolbar buttons.

Restore the do_create_tool_item method, but remove that at the class
level if using PyGObject earlier than 3.7.90.

https://bugzilla.gnome.org/show_bug.cgi?id=686608
https://bugzilla.gnome.org/show_bug.cgi?id=687522
Fix typo.
Merge ../gaupol into gst

Conflicts:
	TODO