Document r269846, vfs.zfs.arc_average_blocksize.

Sponsored by:	The FreeBSD Foundation
Document r269847:
 apr 1.4.8 -> 1.5.1
 apr-util 1.5.2 -> 1.5.3
 serf 1.3.4 -> 1.3.7
 svnlite 1.8.8 -> 1.8.10

Sponsored by:	The FreeBSD Foundation
Document r269968, iscsictl(8) '-M' flag.

Sponsored by:	The FreeBSD Foundation
Document r269975, igxbe(4) tunable renaming.

Sponsored by:	The FreeBSD Foundation