Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Partially merge r240494, which moved netinet/ipfw to netpfil/ipfw,
to make it easier to merge ipfw commits back to stable/9.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Add a priority-based packet scheduler.

Sponsored by: The ONELAB2 Project
Submitted by: Riccardo Panicucci