New experiments with focus.

I came up with a new workaround for computing the actual mouse position
when a focussing click comes in. It's mostly the same only I need
to account for the mac menu bar (and I don't yet know how that'll behave
with HiDPI modes).

But then: it's fucked!
 - Maybe due to the new way the window works, I end up seeing constant
 active/inactive transitions on the Display if I mouse outside of it
 but don't actually focus a new window. These extra transitions back
 to being active totally fuck-up what I'm trying to do here, so don't do
 it if we detect that the mouse is outside of the window.
 - If I force the LWJGL mouse position, it ends up being reflected around
 the Y of the window... WAT? It works elsewhere. So I have to manually
 reflect the Y coordinate or it is REALLY obnoxious with the mouse
 jumping around.
 - And now for some reason it doesn't actually update the mouse correctly
 even when I call setCursorPosition. If I click without movement after
 the focus it goes back to the ORIGINAL location where focus was lost!
 What the flying fuck?

So I guess I'm still screwing with this.

Also:
 - Included an experimental test to see how naive handling would now
 behave on windows. If it allows hovers when not focused, then it's
 not the end of the world to grab the focusing click.
 We may want to keep our focusing-click-is-tossed behavior, but I
 wanted to see how this worked. Note that on MacOSX we do not get
 any kind of mouse moved events when not active so this has no effect
 there.