MILESTONE and BUILD_NUMBER with new build system

[Henri Gomez]

> I recently raised this problem with build-infra. Presently the MILESTONE and
> JDK_BUILD_NUMBER (note name change) are used for these but they get
> overridden by the values in the version.numbers file. So you can either put
> the right numbers in that file, or delete those variables from the file and
> set them via the environment.

It was what I guessed from studying configure stuff.
I'll remove vars from version.numbers for now.

Thanks