MFC r326361: Remove unused include.

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

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

Spelling fixes for usr.bin/

Remove semaphore map entry count "semmap" field and its tuning
option that is highly recommended to be adjusted in too much
documentation while doing nothing in FreeBSD since r2729 (rev 1.1).

ipcs(1) needs to be recompiled as it is accessing _KERNEL private
variables.

Reviewed by: jhb (before comment change on linux code)
Sponsored by: Sandvine Incorporated

Use %zu when printing size_t.

MFC after: 1 month

Make the char *n_name member of struct nlist 'const'.
This avoids errors or __DECONST() from places with higher WARNS levels.

Adjust a local cache variable in ipcs to const as well
to compile in the new world order.

Suggested by: jhb
Reviewed by: jhb, kib, brueffer (man)

Add the ability to clean up all shared memory segments which are
unused in one go.

From the original PR:

I've observed that linux apps running under the linuxulator
have a habit of leaving behind shared memory segments which
are unused, but which eventually cause the system to run
out of free segments and these apps will stop working.
ipcrm(1) currently only allows removal of unused message
queues, shared memory segments and semaphores on an individual
basis, or those having a matching (non-zero) key. However
it would often be convenient to just do a complete cleanup
of everything, usually as root.

PR: bin/118292
Submitted by: Callum Gibson <callumgibson@optusnet.com.au>
Not reviewed by: grog@
Approved by: grog@