[Bf-python] Escaping from Python Scripts

[Campbell Barton]

This one bounced, take 2
 > Somthing that some slower python scripts need to do is to let the 
user Escape during the script.
 > Going into the Console and pressing Ctrl+C isnt that good since it 
can leave the scene in an odd state. and exits messily.
 >
 > Since rendering and radiosity  use the Escape key to exit early.
 > Could we have a function that checks weather the escape key is held? 
maybe as a part of the Window module- could work like Ctrl/Alt/Shift.
 >
 > - Cam
 >