Standardize the COMMENT and pkg-descr with the other gnupg ports.

Readline for everyone instead of it sometimes showing up and never
being recorded.

Don't link gpg to gpg2 on uninstallation. This is not a good idea.
The gnupg{,20} ports handle creating that symlink.

Remove the .sig file from distinfo.

PORTREVISION bump for the dependency and plist changes.