MFC r291329:

Remove redundant DPSRCS which were already in SRCS.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Fix the manual build.

Patches from Ruslam Ermilov to remove NetBSD bits from Makefiles and cleanup
build problems with rescue.

create a new build heirarchy for ipfilter tools