Fix previous differently to avoid over-padding the base64 encoded output,
by being smarter in the decode stage.

clean up various bits of lint, and one outstanding bug:

+ properly terminate base64-encoded output, fixes a bug whereby if the input
length was divisible by 3, a bad base64 encoding would ensue

Add pgp2ssh, a utility to retrieve PGP keys via HKP, and to store the keys
in ssh format. In combination with hkpd (using ssh key files), this utility
can be used to distribute ssh pubkey files to remote computers using the
HKP protocol.