oops... I'm combining two different things in this commit... so I'll try be clear

oops... I'm combining two different things in this commit... so I'll try be clear

1. when another wm requests to replace openbox, openbox exits. but the SM will just restart openbox unless we tell it not to. so now ob_exit_replace() will change the session manager's view of openbox to not restart it. that way the new WM will be able to run.

2. allow windows to move themselves off of the screen 90% of the way, if they really want to. but only 90% to the left, right, and bottom of the screen. it won't let the app move off the top of the screen on its own at all now, since hiding the titlebar on you without you being a part of the process is pretty darn evil!

this is really to address bug # 2982 - for the tilda application. but i guess if windows really want to move off the screen, who's to say no? also, every other window manager will let them - except metacity won't let them on the left/top side of the screen.