Revert "fix problem where the previous code ignored callbacks for properties whose"

This reverts commit 178b5ff626d747026fc9d03c7908c3f203fbd263.

Conflicts:
	ChangeLog
Fix property notifications for certain properties

If a property has a reload function, but the standard property-fetching
mechanism isn't used (hooks->type == META_PROP_VALUE_INVALID), then the
a logic error (introduced in January) caused the hook to never be run.

This meant that changes to struts and icons weren't noticed.

Same as: http://bugzilla.gnome.org/show_bug.cgi?id=572573
The fix here is different in detail from that applied to Metacity, but
similar in spirit.

http://bugzilla.gnome.org/show_bug.cgi?id=585980
window-props: improve properties handling

All changes here are based on mutter.
add support for _GTK_FRAME_EXTENTS

Support for _GTK_FRAME_EXTENTS are based on mutter.