[RP] feature: ignore window `X'

[twb]

Foolishly, I've been playing around with GNOME(1) et al because I just
got a new box that'll run it.

Now I once again have a craving for little CPU and eth1 graphs to tell
me when my console programs are finished.

Now the gnome panel (unlike fspanel) tells RP not to WMify it, so you
can use the ol' <defbarborder L T R B> to make a gap for it.

It occured to me it might be useful to tell RP to ignore specific
windows (more on this in a moment), so that you can move them around
with nawm.

How to identify the windows is a little tricky.  WinID's are unique,
but don't carry across executions (same goes for RP-window-number). 
You could use the WM_NAME string, but it's often yukky and changes for
stuff like xmms.  I think the best identifier to use is the WM_CLASS
class/instance pair.  OOffice & Miscellaneous SDL apps don't set these
usefully, but you're unlikely to use them as monitors :)

just an idea, beat me down if its too wanky.

Trent