INTERACTIVE_CONFIGURE: Launches Configure in its default mode, which is
	*very* interactive. Disabled here by default to conform to FreeBSD
	guidelines, this mode is useful if you have problems with the
	default Configure.

GUI: Disable this to build a headless version of Gtk-Gnutella. Therefore,
	monitoring of operations for Gtk-Gnutella will have to be
	done without relying on any GUI, and the configuration is done via
	files only.

TLS: Enable support for scrambling GNet connections. Currently supported
	only by Gtk-Gnutella.

NLS: Enable National Language Support for translation of User Interface.

IPV6: Enable to support IPv6 connections. The real configuration takes
	place at run-time so keeping it enabled will not force IPv6 usage.

DBUS: Enable D-Bus IPC support. Gtk-Gnutella will send out messages onto
	the D-Bus message bus. That way external applications can easily
	act on certain events that happen, such as a completed download.

DEBUG: Compile with debugging symbols. Useful if you intend to make a
	bug report.

PORTABILITY: Configure code to use the PATH variable at run-time at a
	cost in performance. Useful if you intend to move the executable
	to multiple machines.