directory where an old dma binary can remain

Simplifying maintainance and options (only one place to deal with MK_DMAGENT)

This also makes packaging base less intrusive by getting a single point where
to add tags.

Reduce overlinking

It is a small and lightweight Mail Transport Agent.
It accepts mails from locally installed Mail User Agents (MUA) and delivers the
mails either locally or to a remote destination. Remote delivery includes
several features like TLS/SSL support, SMTP authentication and NULLCLIENT.

Make dma conditional to new WITHOUT_DMA option and make it respect WITHOUT_MAIL

Reviewed by:	peter
Discussed with:	emaste, bz, peter