Proposed function: x-display-usable-bounds

["Adrian Robert" <adrian.b.robert@gmail.com>]

Hi,

On the Mac platform both the Carbon and Cocoa ports face the problem
of determining where on the display to place new frames.  For this it
is helpful not just to know the overall dimensions of the display
(x-display-pixel-width,height) but also the portion of the display
that is not obscured/reserved for the dock and menubar.  I assume this
issue comes up as well on Windows (task bar) and on X desktops such as
Gnome or KDE.

The Carbon port was defining its own function to return (top left
width height) for the usable screen area.  Since it seems relevant for
all platforms, it would seem appropriate to name this function with an
x- prefix, e.g., x-display-usable-bounds, and define it for all
platforms.  As a placeholder implementation, a list (0 0
x-display-pixel-width x-display-pixel-height) could be returned.  See
the thread below for the current Carbon and Cocoa implementations.

http://sourceforge.net/mailarchive/forum.php?thread_name=2CE05DE2-B276-4F80-918B-9C1A28DF169A%40gmail.com&forum_name=emacs-app-dev-