[Pm-utils] Somewhat significant change on pm-utils master git branch

[Victor Lowther]

pm-utils now implements its own service command, which lives in
${PM_UTILS_LIBDIR} and implements just enough functionality to do what
pm-utils needs.  It knows how to work services on LSB compliant distros,
Slackware, and Arch.  Contributions for other distros welcome.

$PATH is setup so that the distro-supplied service command will always
be used in preference to ours.