NetRadiant on FreeBSD

NetRadiant on FreeBSD

NetRadiant was ported to FreeBSD. Thanks to some rework done by TimePath on the global defines, some part was very straightforward. At some point, some issues faced were the same as the ones faced on macOS, so doing this is one step toward macOS support (which is not usable yet due to a feature missing in provided GtkGLExt).

Also, Crunch was fixed to build on FreeBSD too, meaning the support is complete.

GtkRadiant was previously ported to FreeBSD, one and an half year later, NetRadiant is now playing in the same field.

See the merge thread for details about the implementation.