add security/dh (DH key exchange)
dh: clean up function names
dh: larger parameters
dh: print raw secret
add Ruby reimplementation of security/dh
dh: replace with Ruby version

All Ruby installations have 'base64' and 'openssl' in stdlib. Perl's
Crypt::DH has to be dug out from AUR or CPAN...
dh: re-add the --pubkey option
dh: clean up output for `echo foo | dh`