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

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

Remove trailing whitespace per mdoc lint warning

Disussed with: gavin
No objection from: doc
Approved by: joel
MFC after: 3 days

Fix a bunch of typos and spelling mistakes.

mdoc: consistently spell our email addresses <foo@FreeBSD.org>

Reviewed by: ru

mdoc: move CAVEATS, BUGS and SECURITY CONSIDERATIONS sections to the
bottom of the manpages and order them consistently.

GNU groff doesn't care about the ordering, and doesn't even mention
CAVEATS and SECURITY CONSIDERATIONS as common sections and where to put
them.

Found by: mdocml lint run
Reviewed by: ru

Add the ksyms(4) pseudo driver. The ksyms driver allows a process to
get a quick snapshot of the kernel's symbol table including the symbols
from any loaded modules (the symbols are all merged into one symbol
table). Unlike like other implementations, this ksyms driver maps
memory in the process memory space to store the snapshot at the time
/dev/ksyms is opened. It also checks to see if the process has already
a snapshot open and won't allow it to open /dev/ksyms it again until it
closes first. This prevents kernel and process memory from being
exhausted. Note that /dev/ksyms is used by the lockstat(1) command.

Reviewed by: gallatin kib (freebsd-arch)
Approved by: gnn (mentor)