#2398 wm geometry with negative positions wrong

[Mark Roseman]

Specifying a negative x/y position in "wm geometry" does not behave correctly.

e.g. "wm geometry . -20-20"

The correct behavior should be that the right/bottom edges of the window will each be 20 pixels from the bottom right corner of the screen. This is what happens on Windows and X11.

When I try it on Mac OS X, the window is mostly offscreen, with just the top left corner peaking out from the bottom right of the screen.