[Gtkradiant] ZeroRadiant Linux and OSX build system

[Timothee Besset]

The basics of the new build system for ZeroRadiant on Linux and OSX are
done. I've dropped a little status update on the website:

http://www.qeradiant.com/cgi-bin/trac.cgi/wiki/ZeroRadiant

I need to setup a few things to synchronize better between our internal
ZeroRadiant source and the SVN. Another good thing to get done now may
be to start looking at some easy scripts to install/configure the
editor. Ideally I want to distribute a static tree and use some scripts
to do configuration.

TTimo