Change version numbering scheme?

[John W. Eaton]

I propose that we begin using a version numbering system similar to what 
is now used by GCC (https://gcc.gnu.org/develop.html):


Starting with GCC 5 we will bump the major version number for each 
release. The version number and DEV-PHASE will develop in the following 
way and on the following timeline:

Version DEV-PHASE       When

5.0.0   (experimental)  during active development of GCC 5 (stage 1-3)
5.0.1   (prerelease)    during the stabilization period of GCC 5
6.0.0   (experimental)  during active development of GCC 6 (stage 1-3)
5.1.0           for the first release from the GCC 5 branch
5.1.1           during development on the branch post the 5.1.0 release
5.2.0           for the second release from the GCC 5 branch
5.2.1           during development on the branch post the 5.2.0 release
6.0.1   (prerelease)    during the stabilization period of GCC 6
...             

To summarize, the first release of GCC 5 will be GCC 5.1.0 while 
development snapshots will be GCC 5.0.0 and snapshots from the release 
branch GCC 5.n.1.

Rationale

This change allows to more easily identify GCC versions by giving each 
of the development phases distinctive versions. The change also takes 
advantage of the fact that previously the GCC major number carried 
little to no useful information.

My reasons for wanting to make this change:

  * Using this numbering scheme would eliminate the "+"
    from the version number that we have been using.

  * It would also make the major version number meaningful again.

  * And, it would allow us to distinguish the stable development
    version from the released stable version.  We don't currently
    do anything about that, so for example, after we released
    4.2.1, the stable branch also had that version number for
    over a year.

With this numbering scheme:

  * Any version X.0.0 means "this is an experimental development
    version".

  * Any version X.Y.1 means, "this is a pre-release version meant
    for bug fixing and testing".

  * Any version X.Y.0 with Y != 0 means "this is a released version".

Comments?

jwe