Following the guidance in
https://opensource.google/documentation/reference/releasing/authors,
start maintaining an AUTHORS file.

Update all existing Google copyright lines to 'The BoringSSL Authors'
per the document. This CL also changes the styling to match the new
guidance: removed the '(c)' and the comma.

All other existing copyright lines are left unmodified. Going forward,
our preference will be that new contributions to BoringSSL use 'The
BoringSSL Authors', optionally adding to the AUTHORS file if the
contributor desires.

To avoid being presumptuous, this CL does *not* proactively list every
past contributor in the BoringSSL half of the AUTHORS file. Past
contributors are welcome to send us a patch to be added, or request that
we add you. (Listed or not, the commit log continues to be a more
accurate record, and any existing non-Google copyright lines were left
unmodified.)

The OpenSSL half of the AUTHORS file is seeded with the contents of the
current OpenSSL AUTHORS file, as of writing. The current contents in the
latest revision of the 1.1.1 branch
(b372b1f76450acdfed1e2301a39810146e28b02c) and master
(d992e8729ee38b082482dc010e090bb20d1c7bd5) are identical, just formatted
in text vs Markdown.

Note when reviewing: CONTRIBUTING.md and AUTHORS contain non-mechanical
changes.

Bug: 364634028
Change-Id: I319d0ee63ec021ad85e248e8e3304b9cf9566681
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/74149


Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>