net-p2p/microdc2: the port had been improved (manpage location, etc.)

• Obey the new world order and install manpages under ${PREFIX}/share
• Get rid of MANPREFIX reference (override GNU_CONFIGURE_MANPREFIX for now until it can be universally set in the Mk/bsd.port.mk after all ports would be converted)
• Remove dead links from the MASTER_SITES and WWW line, adjust LICENSE
• Claim maintainership: given the troubled history of this port, it is safe to assume that Pavel had not been taking care of it since 2013