Move structs to a 'Private structures' section in ssl.h.

To be consistent with some of the other headers and because SSL_METHOD
no longer has a place to anchor documentation, move the type
documentation up to the corresponding section headers, rather than
attached to a convenient function.

Also document thread-safety properties of SSL and SSL_CTX.

Change-Id: I7109d704d28dda3f5d83c72d86fe31bc302b816e
Reviewed-on: https://boringssl-review.googlesource.com/5876
Reviewed-by: Adam Langley <agl@google.com>
2 files changed