Move the dpv related files from FreeBSD-runtime to a new package named
FreeBSD-dpv
The only consumer is bsdinstall which is already in it's own package.
Reviewed by: bapt, gjb
Differential Revision: https://reviews.freebsd.org/D20960
NB: Should also address `make -j' building
Remove "+" from "+=" in assignments to DPADD/LDADD while here.
NB: Also move CFLAGS for style measure.
Reviewed by: shurd
MFC after: 21 days
X-MFC-to: stable/10 stable/9
X-MFC-with: 274116 274120 274121