(Imported from upstream's 313e6ec11f)

BUG=338886

Change-Id: Id635e78b9afaad5ca311e3aeed888c9aedeb9637
Reviewed-on: https://boringssl-review.googlesource.com/4490
Reviewed-by: Adam Langley <agl@google.com>

Pointer out and suggested by: Ard Biesheuvel.

(Imported from upstream's 5dcf70a1c5)

This is from a while ago, but it's one source of divergence between our copy of
these files and master's.

Change-Id: I6525a27f25eb86a92420c32996af47ecc42ee020
Reviewed-on: https://boringssl-review.googlesource.com/4487
Reviewed-by: Adam Langley <agl@google.com>

This change marks public symbols as dynamically exported. This means
that it becomes viable to build a shared library of libcrypto and libssl
with -fvisibility=hidden.

On Windows, one not only needs to mark functions for export in a
component, but also for import when using them from a different
component. Because of this we have to build with
|BORINGSSL_IMPLEMENTATION| defined when building the code. Other
components, when including our headers, won't have that defined and then
the |OPENSSL_EXPORT| tag becomes an import tag instead. See the #defines
in base.h

In the asm code, symbols are now hidden by default and those that need
to be exported are wrapped by a C function.

In order to support Chromium, a couple of libssl functions were moved to
ssl.h from ssl_locl.h: ssl_get_new_session and ssl_update_cache.

Change-Id: Ib4b76e2f1983ee066e7806c24721e8626d08a261
Reviewed-on: https://boringssl-review.googlesource.com/1350
Reviewed-by: Adam Langley <agl@google.com>

Initial fork from f2d678e6e8 (1.0.2 beta).

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