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

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

Mark global functions and/or variables in fstat(1) static where possible.

This allows compilers and static analyzers to more thorough analysis.

fuser: Fix skipping "SIG" on signal names (-s).

The code did !strncasecmp(str, "sig", 4) which is not useful.

Also change "sig" to "SIG" matching the uppercase signal names as of
r218285. This has little effect because fuser does not enable locale.

- Commit work from libprocstat project. These patches add support for runtime
file and processes information retrieval from the running kernel via sysctl
in the form of new library, libprocstat. The library also supports KVM backend
for analyzing memory crash dumps. Both procstat(1) and fstat(1) utilities have
been modified to take advantage of the library (as the bonus point the fstat(1)
utility no longer need superuser privileges to operate), and the procstat(1)
utility is now able to display information from memory dumps as well.

The newly introduced fuser(1) utility also uses this library and able to operate
via sysctl and kvm backends.

The library is by no means complete (e.g. KVM backend is missing vnode name
resolution routines, and there're no manpages for the library itself) so I
plan to improve it further. I'm commiting it so it will get wider exposure
and review.

We won't be able to MFC this work as it relies on changes in HEAD, which
was introduced some time ago, that break kernel ABI. OTOH we may be able
to merge the library with KVM backend if we really need it there.

Discussed with: rwatson