Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r235140:

General mdoc(7) and typo fixes.

PR: 167713

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Fix typos, spelling, formatting and mdoc mistakes found by Nobuyuki while
translating these manual pages. Minor corrections by me.

Submitted by: Nobuyuki Koganemaru <n-kogane@syd.odn.ne.jp>

You must include fcntl.h (in practice) to be able to do anything useful
with shm_open(2), as otherwise the O_ flags are undefined.

MFC after: 3 days

Add a new file descriptor type for IPC shared memory objects and use it to
implement shm_open(2) and shm_unlink(2) in the kernel:
- Each shared memory file descriptor is associated with a swap-backed vm
object which provides the backing store. Each descriptor starts off with
a size of zero, but the size can be altered via ftruncate(2). The shared
memory file descriptors also support fstat(2). read(2), write(2),
ioctl(2), select(2), poll(2), and kevent(2) are not supported on shared
memory file descriptors.
- shm_open(2) and shm_unlink(2) are now implemented as system calls that
manage shared memory file descriptors. The virtual namespace that maps
pathnames to shared memory file descriptors is implemented as a hash
table where the hash key is generated via the 32-bit Fowler/Noll/Vo hash
of the pathname.
- As an extension, the constant 'SHM_ANON' may be specified in place of the
path argument to shm_open(2). In this case, an unnamed shared memory
file descriptor will be created similar to the IPC_PRIVATE key for
shmget(2). Note that the shared memory object can still be shared among
processes by sharing the file descriptor via fork(2) or sendmsg(2), but
it is unnamed. This effectively serves to implement the getmemfd() idea
bandied about the lists several times over the years.
- The backing store for shared memory file descriptors are garbage
collected when they are not referenced by any open file descriptors or
the shm_open(2) virtual namespace.

Submitted by: dillon, peter (previous versions)
Submitted by: rwatson (I based this on his version)
Reviewed by: alc (suggested converting getmemfd() to shm_open())

Sort sections.

Fix the NAME section making whatis(1) happy in particular.

Mechanically kill hard sentence breaks.

mdoc(7) police: Use the new .In macro for #include statements.

MFS: in HISTORY section, fix release number of first appearance

``.St -p1003.1b'' -> ``.St -p1003.1b-93''.

mdoc(7) police: Nm -> Fn where appropriate.

mdoc(7) police: use certified section headers wherever possible.

Whitespace only change: trim trailing whitespace.

Spell MAP_NOSYNC correctly.

Submitted by: allenc@verinet.com

.Lb-ify

Add shm_open(3) and shm_unlink(3). The documentation could use a good
bit of work (and is stylistically probably the worst manual page
I've ever written).