The prior code was checking string constants (which are #defines from
configure) against NULL. They can never be NULL, so the checks were
overly-defensive. If the preprocessor macros do not exist, we'll get
a different compiler error. So remove the dead code.
This fixes CID 72349.
Update the VERSION file scheme:
* Remove "want_repo_rev".
* Add "tarball_version".
All values are now always included (major, minor, release, greek,
repo_rev). However, configure.ac now runs "opal_get_version.sh
... --tarball", which will return the value of tarball_version (if it
is non-empty) or the "full" version string (i.e.,
"major.minor.releasegreek").
