Change all coordinate variables from "unsigned short" to "short".

Change all coordinate variables from "unsigned short" to "short".
Implement operations needed to draw lines and points in windows, to
determine the capabilities of the display, and to change the title bar
of a window.  Extend the window-opening procedure to allow the window
style to be specified.  Change PM primitives to allow multiple event
queues, so that messages for graphics windows can be kept separate
from messages for Edwin windows.