Reorganization of the header files (GitHub #9333)

[Dr. Matthias St. Pierre]

Hi,

some of you might have loosely followed pull request #9333 (see [1]),
where I am reorganizing the header files in a more consistent manner.

Since I intend to do the reorganization both to master and the 1.1.1
stable branch (in order to facilitate conflict-free cherry-picking to 
the 1.1.1 LTS branch), I decided to automate the changes. This decision
turned out to be very convenient, because the heavy rearchitecturing on
master frequently conflicted with my changes. Instead of resolving
conflicts, I could just rerun the script after rebasing.

When this pull request finally gets merged, it might happen that you
in turn encounter more merge conflicts as usual, in particular if you
are one of the 'replumbers' involved in the FIPS rearchitecturing.
It might also happen if you are working on some long running pull
request like the CMP integration.

To check the impact of my changes on your work, I did some rebasing
experiments, and as a result I wrote down some guidance about possible
rebasing strategies in [2].

The reason I write this mail is because I'd like to hear your opinion
about how to proceed with this pull request. There are two possibilities:

Variant I):
    Merge early in to get the reorganization integrated as soon
    as possible and not wait until shortly before the next release.

Variant II):
    Wait a little bit more until the heavy rearchitecturing
    has settled down a little bit.

What is your opinion? What are your preferences?


Regards,

Matthias


[1] https://github.com/openssl/openssl/pull/9333
[2] https://github.com/openssl/openssl/pull/9333#issuecomment-536105158