PyPanel

Adds autohiding when mouse is moved out of window.

In the current version of pypanel, the pypanel panel is hidden after
several seconds (CLOCK_DELAY) of inactivity. This patch adds behavior to
hide the panel as soon as the mouse moves out of the panel, rendering the
clock delay useless.

I'm certain more work could be done to combine the two (i.e., start the
hide delay when the mouse moves out of the panel), but I don't have the
time or interest to do that right now. It seems to me that such an idea
would require ugly work with threads and sleeping anyway, though I could
well be wrong.

Anyway, I'm happy how it turned out, I hope someone else finds it useful.