Cleanup
libgui|KeyEvent: Added key modifiers into a key event

The input source may provide information about which keyboard
modifiers were active at the time of a key press/repeat.
Refactor|libshell|AbstractLineEditor: Don't assume control mod is active

Now that information about the Control modifier is included in the
event, there's no need to assume that it's active when handling an
editor control key.
Client|Widgets: New widgets use native keyboard repeat events

The old key repeat system does not work when frame rate is too low.