Converserely, when the icon is clicked, the icon needs to be hidden on the backgound and the window needs to be restored in its current state (which may be different than the state of the window at the time it was iconified.
Squashed commit of the following:
graphics/: Add checks in all places that I can think to avoid doing something stupid with hidden windows
Improve some naming
Add a new file missing in last commit.
graphics/: Initial, incomplete support for hiding windows.
graphics/nxbe/nxbe_bitmap.c: Fix another coordinate system problem.
graphics/: Review use of device coordinate system with window frambebuffer and make fixes accordingly.
graphics/nxbe/nxbe_fill.c: Fix a coordinate system bug. Was trying to update the window fraembuffer using the device coordinate system. Need to use the relative coordinate system.
graphics/: Use DEBUGASSERT instead of return an error since the is no user to handle the errors within the NX server. Use CONFIG_DEBUG_GRAPHICS instead of CONFIG_DEBUG_FEATURES in most cases.
graphics/: Nothing under graphics/ should set the errno.
