Define per-screen groups

This should make Xinerama-aware screens behave independently of each other
when switching groups.
Init and use FIFO for status output

This introduces the ability for CWM to output information down a named FIFO
when status events happen.  Currently, the scope of this is quite limited
but it provides just enough information to be useful.

There is one FIFO per screen defined, which should make separating out
events per screen easier.
Call u_put_status() from key parts of CWM

This adds in calls to u_put_status() for certain CWM events.  Most notably, the
creation of new windows, changing focus, PropertyNotify events causing a change
in XA_WM_NAME, and switching of groups, etc.
Add example CWM -> dzen2 perl script

This is a proof-of-concept script showing how the status output from CWM can be
turned in to something which dzen2 can use to display different pieces of
information.
Expand a client

This expands a client to fill all space around another client.

As a consequence, this patch also includes crude support for per-group
Xinerama-aware clients, so as not to affect other clients on other monitors
when expanding a client.