Add two new entity files in followup to r265590,
sponsor.ent and vendor.ent, which will be used for
sponsor/vendor names and URLs.

Sponsored by:	The FreeBSD Foundation
Add references to sponsor.ent and vendor.ent in
relnotes/article.xml and share/xml/catalog.xml.

Sponsored by:	The FreeBSD Foundation
Add sponsorship attribution for r258838 (casperd(8)).

Sponsored by:	The FreeBSD Foundation
Add attribution for r258884.
Add DARPA, AFRL to sponsor.ent.

Sponsored by:	The FreeBSD Foundation
Add attribution for r264601.

Sponsored by:	The FreeBSD Foundation
Add attribution for r265236.
Add LSI and Spectra Logic to sponsor.ent.

Sponsored by:	The FreeBSD Foundation
Add attribution for r265348.
Add Netgate to sponsor.ent.

Sponsored by:	The FreeBSD Foundation
Add a note to keep the entity lists sorted alphabetically.

Sponsored by:	The FreeBSD Foundation