[dev] [dwm] pull request: tagnames per monitor

Hi list,

attached pull request (against 1528:b4f5309d6253) allows to name the tags for
each monitor. You can name your tags for as many monitors as you like.
If you still have less monitors, it uses the last defined as a fallback
for these.
Also included is a slight modification of Evan Gates' nametag pull request to
rename tags while dwm is running.

I appreciate any comments.

-- 
Thomas Dahms