Problem is is with operator redo which click-extrude exposed.
Check if redo operator can run, otherwise lock the UI and add a label that the operator doesn't support redo.
This is clunky but IMHO better then failing silently and leaving the user confused.
- Merged redo functions into ED_undo_operator_repeat(), code was duplicated in a few places.
- added WM_operator_repeat_check to check if WM_operator_repeat() can run, avoids an undo call when redo work.
Unrelated changes
- GHOST_SystemWin32.cpp set to utf8 encoding.
- cmake_consistency_check.py now checks source files are utf8.
