units(1): Add some some additional units

Most of these are also recognized by GNU units
units(1): fix spelling

Pointyhat to:	me
Add support for UDP-Lite protocol (RFC 3828) to IPv4 and IPv6 stacks.
Tested with vlc and a test suite [1].

[1] http://www.erg.abdn.ac.uk/~gerrit/udp-lite/files/udplite_linux.tar.gz

Reviewed by:	jhb, glebius, adrian
Minor style cleanups.
Add man page for udplite(4).