pointer grabs should time out

[Mike Hearn]

> Once the app dies yes. But if you had to kill the app it wasnt dead 8)

Zero points to me for in the "thinking before speaking" round.

So, I think the only way to solve this is for the WM to ping whichever 
app is holding the server grabbed and if it stops responding, to break 
the grab. Right now metacity only pings the app when you ask it to 
close, I suppose to avoid keeping all the different programs paged in 
when not being used.

Only one app at a time can grab the server though, so pinging the app 
makes sense.

I can't remember what exactly is dropped when a server is grabbed. I 
think it is everything, so maybe an extension could be made so that the 
WM can ping even when the server is grabbed.