Add maximized protocol

Add maximized protocol

A request from the client to ask the compositor to maximize the surface.
The compositor will reply with a configure event telling
the expected new surface size.  The operation is completed on the
next buffer attach to this surface.

A maximized client will fill the fullscreen of the output it is bound
to, except the panel area. This is the main difference between
a maximized shell surface and a fullscreen shell surface.