MILESTONE and BUILD_NUMBER with new build system

[Henri Gomez]

> Just on one point, the system should automatically determine if you need to
> re-run configure. It notices if you need to re-run autogen, so I would
> expect it also notices when configure needs to be re-run. That said I
> haven't tried it.
>
> It is also unclear to me when you can just re-run configure in an existing
> configuration and when you must "dist-clean" and start again.

By removing vars in version.numbers,  I've now expected behaviour :

OpenJDK Runtime Environment (build 1.8.0-lambda-b56-20120925)
OpenJDK Server VM (build 24.0-b21, mixed mode)
openjdk version "1.8.0-lambda-b56"

About version and configure, +1 to have them set from the outside,
version.numbers and env vars override.
configure should be use to configure build chain, not to set
informations like version, company.

My 0.01$