qa/admin/check-vm - tweak list of things to check
linux_proc pmda - refactor procfs error handling

Clean up the error handling
- be algorithmicly consistent across all the fetch_* methods
- confine the system call error code mapping to a new maperr()
  static function

Note, this makes the error handling sane and consistent.  It is unclear
what the access control semantics should be.  With this change, the
Linux proc PMDA returns the following info ...

- all processes if installed as a daemon PMDA and run as root
- all processes belonging to the uid of user "pcp" if installed
  as a DSO PMDA (needs special hacking as the default Install
  script does not support this mode of installation)
- all processes belonging to the user if using PM_CONTEXT_LOCAL,
  e.g. with -L and -K to pminfo

If this is not what's expected, we need to talk.
Looks like not.a.real.host now resolves to a real address too

Sick puppies.  Use the same approach kenj used for no.such.host.
Merge branch 'dev' of git://git.pcp.io/kenj/pcp into dev