nant build with linux

hi

I checked in a updated version of the nant build file.
Since mono 0.28 and recent nant versions. it's possible to use nant with 
mono/linux.

SWT/GTK is building currently with nant.
The glue library has it's own buildfile, but since I'm not a nan't guru 
and havn't time to get one currently, the build file calls make to do 
the work.

I didn't change the win32 part of the buildfile.

@Roman: probbably you are able to update (if needed) this for freebsd?

greethings

Dominik