Previously, public headers lived next to the respective code and there
were symlinks from include/openssl to them.

This doesn't work on Windows.

This change moves the headers to live in include/openssl. In cases where
some symlinks pointed to the same header, I've added a file that just
includes the intended target. These cases are all for backwards-compat.

Change-Id: I6e285b74caf621c644b5168a4877db226b07fd92
Reviewed-on: https://boringssl-review.googlesource.com/1180
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>

This change stops the Intel, SHA instruction code from breaking the
Windows build.

PR: 3405

(Imported from upstream's 1f6d207625)

(Imported from upstream's 70fddbe32a)

(Imported from upstream's d00ae7cf70)

(Imported from upstream's f92926e331)

(Imported from upstream's 729d334106)

Initial fork from f2d678e6e8 (1.0.2 beta).

(This change contains substantial changes from the original and
effectively starts a new history.)