nv(3) was not in 10.0.

It might be MFC'd to stable/10 for 10.1, but for now update the manual to
avoid confusion on its availability.

Discussed with:	pjd
Fix breakage in ipfw+VIMAGE after r261590.

PR:		kern/187665
Sponsored by:	Nginx, Inc.
Add change forgotten in r263475.  Make dmaplimit accessible outside
amd64/pmap.c.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Mark the following sysctls as MPSAFE:
kern.file
kern.proc.filedesc
kern.proc.ofiledesc

MFC after:	7 days
Merge remote-tracking branch 'upstream-github/master' into soldierx/lattera/aslr