bugs 454312 and 454417: fix gv when selecting backwards, fix vi visual mode mouse selection
Fixes for:
- https://bugs.kde.org/show_bug.cgi?id=454312 Kate Vi mode mouse selection makes cursor position wrong (always +1 column)
- https://bugs.kde.org/show_bug.cgi?id=454417 'gv' can't select last selection sometimes in Kate Vi input mode
Unfortunately, the fixes for the 2 of these depend on each other so I can't make it a separate MR.