* mu-register.el (mu-cite-load-registration-file): Reverted. I've got XEmacs

* mu-register.el (mu-cite-load-registration-file): Reverted.  I've got XEmacs
 wrong that it does'nt support the coding system magic cookie.  However it has
 been working since XEmacs 21.2.21.  Users can avoid mis-decoding a file by
 setting the value of the option `mu-registration-file-coding-system-for-read'
 properly even if they are using one of old (X)Emacsen.
(mu-registration-file-coding-system-for-read): Fix a doc-string.