doc: Suggest the use of strconcat for recipient strings.
doc: Suggest the use of strconcat for recipient strings.

--
GnuPG-bug-id: 3775

Signed-off-by: Werner Koch <13bd1fc5137f503b0a8355ad400e7a87ebb45b25@gnupg.org>

gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme