[xmonad] darcs patch: spawnDescendantOn

[wagnerdm at seas.upenn.edu]

Quoting Spencer Janssen <spencerjanssen at gmail.com>:

> I notice some use of /proc, that will fail under non-Linux, right?

Maybe.  I based the implementation on the information here:
http://www.steve.org.uk/Reference/Unix/faq_2.html#SEC17
which suggests that parsing /proc is the cleanest way when it works.   
If someone on a BSD could give a sample /proc/PID/status file, that  
would of course help.

> Also, can we mostly avoid the need for all this by 'exec'ing scripts?

Some of it can be avoided this way, yes, and I believe that's what  
spawnOn attempts to do, in a somewhat hacky way.

~d