[style] Make the resize-grip a bit nicer
[style] Make the resize-grip a bit nicer

Taper off the corner of the resize grip that's inside the window, looks
a little nicer.

clutter-project/mx,clutter-project/mx,clutter-project/mx,jonnylamb/mx,pwithnall/mx,pwithnall/mx,jonnylamb/mx,clutter-project/mx,jonnylamb/mx,pwithnall/mx,pwithnall/mx,jonnylamb/mx