Protocols.SMTP.Client()->send_message() lets bare LF's slip through

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=4483

Reported by Mathias Södermark mathias@roxen.com

Protocols.SMTP.Client()->send_message() does not convert bare LF's to CR-LF or throw an error that they are not allowed.