The only use of sbrk in libgtop is in an example which always calls it
with 0. Since the use of sbrk provides no functionality, just skip these
calls when sbrk is not available.

This problem was first reported on FreeBSD Bugzilla because FreeBSD
decides not to support sbrk on ARM64 and RISC-V:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=221751

Fix #46

Code in sysdeps/freebsd contains a lot of HAVE_KINFO_GETFILE checks, but
the macro is always undefined because the configure script doesn't check
for it. To fix it, add required checks for kinfo_getfile function.

This function isn't exported so it should be skipped.

gjs#259

The use of AM_GNU_GETTEXT_VERSION in configure.ac instructs autopoint to
copy po/Makefile.in.in from the exact gettext version. It is fine if the
version of gettext installed on the system has the same minor version
number with the requested version, but it fails if you have a newer
version of gettext because of the mismatch between autoconf macros and
Makefile.in.in.

  *** error: gettext infrastructure mismatch: using a Makefile.in.in
  from gettext version 0.19 but the autoconf macros are from gettext
  version 0.20

Instead of specifying the exact version with AM_GNU_GETTEXT_VERSION, we
can use AM_GNU_GETTEXT_REQUIRE_VERSION to ask autopoint to simply use
the gettext version installed on the system to prevent the mismatch.

This also bumps the version requirement on gettext to 0.19.6 because
AM_GNU_GETTEXT_REQUIRE_VERSION was added in this version.

See https://wiki.gnome.org/Projects/GnomeCommon/Migration

freebsd: Support laundry memory and ZFS ARC

See merge request !3

FreeBSD 11.1 removes cache memory and adds laundry memory. The MIB of
cache memory still exists, but its value is always set to zero.
According to the man page of top(1), the value of laundry memory means
number of dirty pages queued for laundering, suggesting that it should
be added to the 'user' in libgtop because it cannot be freed immediately
without writing out data. Laundry memory was part of inactive memory in
older FreeBSD releases.

FreeBSD systems running on ZFS usually have a large portion of memory
used as ZFS ARC, which has similar purpose to buffer cache of other
filesystems. ZFS ARC can usually be freed quickly when the system needs
more memory, so we don't want to put it in 'user' in libgtop. However,
both buffer cache and ZFS ARC are parts of wired memory, and wired
memory is counted in 'user'. Therefore, we subtract the size of ZFS ARC
from wired memory when calculating 'user' value, making it more useful
to FreeBSD users.

This patch is based on the patch submiited three years ago by
Benoît Dejean <bdejean@gmail.com>.

https://bugzilla.gnome.org/show_bug.cgi?id=748928
#31

Revert this proof of concept.
Add C file with comments to document how to make a call SUID.

Add suid infrastructure.
Demo proc_map.

The previous name is incorrect and inconsistent with the code generated
by lib.pl.
Also add missing hooks.

This symbol, although exposed in public headers is not part of the API
and is only used internally.

#36