Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

These files were getting sys/malloc.h and vm/uma.h with header pollution
via sys/mbuf.h

The r48589 promised to remove implicit inclusion of if_var.h soon. Prepare
to this event, adding if_var.h to files that do need it. Also, include
all includes that now are included due to implicit pollution via if_var.h

Sponsored by: Netflix
Sponsored by: Nginx, Inc.

Fix memset sizeofs

Reviewed by: bschmidt

Fix typos - remove duplicate "is".

PR: docs/154934
Submitted by: Eitan Adler <lists at eitanadler.com>
MFC after: 3 days

correctly set the tailq ptr when removing the last item in the q

Approved by: re (kensmith)

Add ieee80211_ageq; a facility for staging packets that require
long-term work before they can be serviced. Packets are tagged and
assigned an age (in seconds) at the point they are added to the
queue. If a packet is not retrieved before it's age expires it is
reclaimed. Tagging can take two forms: a reference to an ieee80211_node
(as happens in the tx path) or an opaque token in cases where there
is no reference or the node structure is not stable (i.e. it's going
to be destroyed).

o add ic_stageq to replace the per-node wds staging queue used for
dynamic wds
o add ieee80211_mac_hash for building ageq tokens; this computes a
32-bit hash from an 802.11 mac address (copied from the bridge)
o while here fix a stray ';' noticed in IEEE80211_PSQ_INIT

Reviewed by: rpaulo
Approved by: re (kensmith)