In OpenSSL builds, declare STACK for datatypes ...

In OpenSSL builds, declare STACK for datatypes ...

... and only *define* them in the source files that need them.
Use DEFINE_OR_DECLARE which is set appropriately for internal builds
and not non-deprecated builds.

Deprecate stack-of-block

Better documentation

Move some ASN1 struct typedefs to types.h

Update ParseC to handle this.  Most of all, ParseC needed to be more
consistent.  The handlers are "recursive", in so far that they are called
again and again until they terminate, which depends entirely on what the
"massager" returns.  There's a comment at the beginning of ParseC that
explains how that works. {Richard Levtte}

Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/10669)