Document procedure of regenerating generated-configure.sh in JDK8, using auotconf

* which versions of autoconf are acceptable for JDK 8 build
* command to regenerate generated-configure.sh
* Should you ever merge the generated-configure.sh, or regen before integrating.
* avoiding mismatches between open and closed.

>> In most cases, regenerating will work fine after merge and I would prefer it being done that way. (for now)
>
> Is there documentation on how the regeneration should be done for both generated config files?
>
> common/autoconf/generated-configure.sh
> jdk/make/closed/autoconf/generated-configure.sh
>
> Is it just running autogen.sh in both of the autoconf directories?

If you are at the top of your source tree, 'bash common/autoconf/autogen.sh' will regenerate both open and closed generated-configure.sh files (assuming you have the closed subtrees...).

> I don't see a copy of autoconf in /java/devtools, where is the version we've been using?

I am using:

/usr/bin/autoconf --version
autoconf (GNU Autoconf) 2.68


Others use version 2.67 which is OK. Both versions work fine, but the diffs end up filled with mostly irrelevant noise. That is why we suggest you not look at the diffs too hard - merge the .m4 files and re-run configure.