Add RFC 5864 to the protocol documentation directory

Add RFC 5864 to the protocol documentation directory

Add a copy of RFC 5864 (DNS SRV Resource Records for AFS) to the
protocol documentation directory for reference.  As permitted by
the IETF Trust License Policy section 3(e), I release this document
under the MIT/X Consortium license included in this copy of the
document.

LICENSE MIT

Change-Id: I8e22aac07b4cedbe18b8375213a7866cf98a1386
Reviewed-on: http://gerrit.openafs.org/1799
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>