Support 'info proc' for native FreeBSD processes.

Support 'info proc' for native FreeBSD processes.

- Command line arguments are fetched via the kern.proc.args.<pid>
  sysctl.
- The 'cwd' and 'exe' values are obtained from the per-process
  file descriptor table returned by kinfo_getfile() from libutil.
- 'mappings' is implemented by walking the array of VM map entries
  returned by kinfo_getvmmap() from libutil.
- 'status' output is generated by outputting fields from the structure
  returned by the kern.proc.pid.<pid> sysctl.
- 'stat' is aliased to 'status'.

gdb/ChangeLog:

	* configure.ac: Check for kinfo_getfile in libutil.
	* configure: Regenerate.
	* config.in: Regenerate.
	* fbsd-nat.c: Include "fbsd-tdep.h".
	(fbsd_fetch_cmdline): New.
	(fbsd_fetch_kinfo_proc): Move earlier and change to return a bool
	rather than calling error.
	(fbsd_info_proc): New.
	(fbsd_thread_name): Report error if fbsd_fetch_kinfo_proc fails.
	(fbsd_wait): Report warning if fbsd_fetch_kinfo_proc fails.
	(fbsd_nat_add_target): Set "to_info_proc" to "fbsd_info_proc".