[A-4762] Spack 3.7 Released

Looking for a quite simple but complete package manager for your distribution or an efficient and daily viable alternative for the Slackware(R) pkgtools? Take a seat.

=== 3.7 (20120513)

+ spackadd: look for and use the "ldconfig" command in $ROOT, not the
one of the system.
(thanks to appzer0 for the suggestion)

+ spackcook: search and strip "ar" archives.
(thanks to appzer0 for the suggestion)

+ spackcook: more portable cleaning routine, using the "ps" command
instead of procfs.

= spackcook: remove the .ownerships file after having applied it.

= spackcook: set the TMPDIR environment variable for spackpkg, so it
uses the right temporary directory for its intermediate packaging
steps.

= spackcook.8: minor fixes and improvments.

Currently, the project is under heavy development, so some features are just partially implemented and some compatibilities issues can be met in certain commands.