[Paraview] Changes to ParaView version policy

[Utkarsh Ayachit]

Folks,

For the longest time ParaView has been using an odd/even version
number scheme: N.{odd}.* was treated as a development version while
N.{even}.* was treated as a release version. There were a couple of
problems:
* One could never tell two development checkouts apart. Since
development version almost was never changed until the next release,
for users reporting bugs on development version it was hard to
determine if the bug was already fixed since the report.
* Manual updates to version number was error prone.

In a previous post (http://markmail.org/message/vbtbjgyt5k5iaanp) on
Apr 15, 2011, I alluded to a possibility of changing ParaView version
scheme.  Accordingly, I've committed a change to git (awaiting
gatekeeper review) to change the version scheme.

Now the version is determined using a call to "git describe"
(http://www.kernel.org/pub/software/scm/git/docs/git-describe.html).
Due to the way the official releases are tagged, this returns a string
in the following form:

v<Major>.<Minor>.<Patch>-<commit count>-<commit sha>

If the source state is same as a tagged official version, then the
string returned will not have anything after the patch version. If
there are any commits since the latest tag, it will result in the
unique suffix.
The advantages are:
* One knows exactly the revision of ParaView source that was used for the build.
* Source does not need to be changed, one simply tags the repository
and the version number is updated.

After 3.12, we no longer need to have even minor numbers for releases,
so if we want, we can release a 3.13, 3.14 and so on.

Utkarsh