[Gtkradiant] ZeroRadiant preview builds

[Timothee Besset]

I've been looking at the process of getting official binaries compiled
and released for ZeroRadiant. We're not there yet but things are coming
together. I've put together 3 zip files for the various platforms:

http://zerowing.idsoftware.com/ZeroRadiant-x86-20080405.zip (32 bit Linux)
http://zerowing.idsoftware.com/ZeroRadiant-x64-20080405.zip (64 bit Linux)
http://zerowing.idsoftware.com/ZeroRadiant-win32-20080407.zip (Windows)

Eventually those will be a little installer with some license prompts,
the content in the included gamepaks requires agreeing to a non-GPL license.

Those zips come with support for Quake III Arena (and mods), and for
Urban Terror standalone version. When you first start the editor it will
prompt to configure the games. You give it a bit of information, and it
will generate a <configured game>.game file with the paths to use. It
will also copy out some stuff into the game directory.

The Windows version seems to have a problem with copying the gamepak
onto the game directory, but since this is all preview stuff at this
point I've included it too.

I am not posting those builds on the site, because at this point we
should still improve the game configuration part and do installers. Also
want to check basic compatibility of the various binaries before we do
any of that.

There are bits of a TODO list and some compiling instructions on the
ZeroRadiant page: http://www.qeradiant.com/cgi-bin/trac.cgi/wiki/ZeroRadiant

TTimo