lib-mail: ostream-dot API changes The dot-line sending is now done when o_stream_flush() is called. This should be used instead of relying on close() doing it, because it still needs to write a few bytes and there are no guarantees that the parent stream allows sending them. Also added force_extra_crlf parameter, which specifies whether CRLF should always be written before the dot-line, even when it already contained CRLF. This is useful if the input is read with i_stream_create_dot(send_last_lf=FALSE), since it allows sending a stream that doesn't have to end with LF.

Implemented dot output stream. This outputs data in the dot-escaped format needed for the SMTP data command. The sequence CRLF.CRLF is sent upon closing the stream.