[dwm] NMASTER feature appeared in hg tip

Hi there,

I implemented two actions in hg tip:

- MODKEY-plus (increaes the clients of master area by 1)
- MODKEY-minus (decreases the clients of master area by 1)

zoom() in stack area works as we know it, it brings the selected
client to the top of master area (first client of master area)

zoom() in master area swaps the specific master client with the
top client of the stack.

Here is a screenshot of this functionality (note that the LOC
has not increased so much because dotile has been simplified a
bit in the inner loop.

http://suckless.org/shots/dwm-20070105.png

Feedback and testing of this change is highly welcome.

Regards,

-- 
 Anselm R. Garbe >< http://suckless.org/~arg/ >< GPG key: 0D73F361