Add '%T' placeholder for filename pattern to insert window title.
Example filenames for pattern %Y-%M-%D %H-%m-%S. %T:
2018-02-21 19-11-55. romas : byobu.png
2018-02-21 19-12-20.png
Example filenames for pattern %T:
romas : byobu.png
Screenshot.png
Closes T8036
FEATURE: 378463
FIXED-IN: 18.04.0