HPUX 11.11 does not support -z flag to tar

HPUX 11.11 (and others?) need to use gzip to manage compressed tar (tgz) files, as their version of tar does not support -z.
Merge multiple constants into a single one

SUNOS and HPUX are only used to identify if tar is bad on that platform.  WIN32 is also used elsewhere.  Identify platforms with a known bad tar program in a single location.
Merge pull request #325 from MidLifeXis/hpux_11_11_tar_does_not_support_z

HPUX 11.11 does not support -z flag to tar