This is a bit of cleanup that probably should have been done at the same time
as 30ddb434bf.
For now, version negotiation is implemented with a method swap. It also
performs this swap on SSL_set_session, but this was neutered in
30ddb434bf. Rather than hackishly neuter it,
remove it outright. In addition, remove SSL_set_ssl_method. Now all method
swaps are internal: SSLv23_method switch to a version-specific method and
SSL_clear undoing it.
Note that this does change behavior: if an SSL* is created with one
version-specific method and we SSL_set_session to a session from a /different/
version, we would switch to the /other/ version-specific method. This is
extremely confusing, so it's unlikely anyone was actually expecting it.
Version-specific methods in general don't work well.
Change-Id: I72a5c1f321ca9aeb1b52ebe0317072950ba25092
Reviewed-on: https://boringssl-review.googlesource.com/2390
Reviewed-by: Adam Langley <agl@google.com>
0f1e64bf7f