Merge changes made in Gnus trunk.

Merge changes made in Gnus trunk.

auth-source.el (auth-source-save-secrets): New variable to control if secret tokens should be saved encrypted.
 (auth-source-netrc-parse, auth-source-netrc-search): Pass the file name to `auth-source-netrc-normalize'.
 (with-auth-source-epa-overrides): Add convenience macro.  Don't depend on the EPA variables being defined.
 (auth-source-epa-make-gpg-token): Convert text to a "gpg:" token.
 (auth-source-netrc-normalize): Convert "gpg:" tokens back to text in the lexical-let closure.
 (auth-source-netrc-create): Create "gpg:" tokens according to `auth-source-save-secrets'.