[dwm] patch to hide sticky indicators, and add "nofocus" windows

I do a lot of roaming, and long story short, nm-applet is nearly a
requirement for me. No biggie, I just run it in stalonetray and set
it to all tags, shoved up in the corner, only I've ran into two
little issues:

1) sticky windows put an indicator on every tag in the bar. I know
   it's on every tag, I put it there, tell me something I don't know.
   The patch hides any window which has tags=~0 from the indicators.
     ( this is simply the 2 lines in drawbar() )

2) since it's on every tag, every time i switch tags, it is the first
   thing focused. I dont need to type into a system tray, so the
   patch also adds a flag to designate a window as "nofocus" which
   tells dwm to skip it when trying to find a window to focus.

   To do this, I had to add a way to designate a window as nofocus, so
   Rule.isfloating is now a bitmask Rule.flags, with enums for the 3
   settings right now: Normal, Floating, NoFocus.

So my config.h, for example, has this Rule:
   { "stalonetray", NULL, NULL, ~0, Floating|NoFocus },

Patch against tip attached, if anyone else is interested - it only adds 7
lines so its still nice and small. =)

Jeremy