Fold away SSL_PROTOCOL_METHOD hooks shared between TLS and DTLS.

The ctrl hooks are left alone since they should just go away.
Simplifying the cipher story will happen in the next CL.

BUG=468889

Change-Id: I979971c90f59c55cd5d17554f1253158b114f18b
Reviewed-on: https://boringssl-review.googlesource.com/4957
Reviewed-by: Adam Langley <agl@google.com>
6 files changed