Created new SMBLIB function: smb_msg_is_utf8() which reutrns TRUE if the passed

message body is UTF-8 encoded. This works for either messages received via FTN
(with the "CHRS: UTF-8" control paragraph) or MIME-encoded messages (e.g.
Internet e-mail).

This is to be used by things to display messages. If the viewer (e.g. user's
terminal) supports UTF-8, just send through as-is. If not, translation (e.g. to
CP437) or filtering may be needed.