This fixes keyToMouseShape (the new handler for mouse shape state for
key combinations, e.g. during mouse tracking override or rectangle
select) so that it respects whether or not the mouse is currently
hidden, and will not send back a shape to change the mouse to in these
situations.
Fixes#1107.
This work is mainly targeted at adding the crosshair for when
ctrl/super+alt is pressed. We also add this for when mouse tracking is
enabled so that we show the crosshair when ctrl/super+alt+shift is
pressed at the same time.
I've also changed the event processing logic here because the amount of
keys we have to process has greatly increased. Instead of processing
each individual event, we now process the modifier state.
Additionally, some refactoring has been done geared at starting to
re-work the mouse for the core surface into a something stateful. My
hope is that we can continue to unravel some of this from the core
surface so that we can process key inputs, motion events, and anything
else relevant as inputs to transitions for shape display, click
behavior, etc.
This commit now also moves the ctrlOrSuper handlers to respective parts
in the Key hierarchy, while also adding additional helpers for other
modifiers.
