failed if a user didn't have the development versions of those libraries
installed; in particular, they tried to compile a GTK+ program and looked for
pkg-config's .pc files. It is better to err on the side of building Zenmap when
it may not be supported than not building it when it may in fact be supported
(which was the previous behavior anyway). See discussion at
http://seclists.org/nmap-dev/2008/q4/0054.html.
Windows and UNIX, and install/distro system for the source tarball, RPM, OS X
installer (thanks to David) and the Windows installer.
configure --without-ncat keeps it out on Unix