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

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

Mechanically substitute flags from historic mbuf allocator with
malloc(9) flags within sys.

Exceptions:

- sys/contrib not touched
- sys/mbuf.h edited manually

Don't update if_obytes when transmitting packets. That is already done
in IFQ_HANDOFF() when the packet is passed to the start routine, so doing
it here resulted in double counting.

Reported by: Alex Tutubalin lexa lexa ru
MFC after: 1 week

- Merge in OFED 1.5.3 from projects/ofed/head