Changing engine to support modifier keys?

I'd like to modify the engine to directly support modifier keys, so that I can do this:

moveMap.bindCmd(keyboard, "shift", "$pShip.gun.fire();", "$pShip.gun.fireStop();");

Currently, you can't do that to receive events when *only* a modifier key is pressed. You can only get notified when a modifier *and* some other key is pressed. I need notifcation for modifier keys alone.

Before I go and start trying to modify the engine, I figured I'd ask if anyone here has already done the same thing. No sense in reinventing the wheel.

If no one has, could someone point me to the appropriate files to look at? I've never dug around in the TGB source before, and with like 400 files getting compiled, I'm guessing a pointer or two could help. ;-)