[WIP] Add openssl ssl.py bindings (Refs #77)

Not sure I'm doing this right - there seems to be a lot more stuff in https://github.com/exarkun/opentls/blob/b38a0cb646c34fe272fd747d6ec096416e279ef8/tls/c/ssl.py, and some of it seems repeated/doesn't match ssl.h.

Tried to keep different types of discrepancies in different commits.

Of particular interest are:

1. https://github.com/cyli/cryptography/commit/cb95bb05d5c6a212f9bb4ed73268d0654b813533
2. https://github.com/cyli/cryptography/commit/441c9f45f9f5050e39944ae17e968fc22275c2ac
3. https://github.com/cyli/cryptography/commit/65a90e3dba392a589e9467a12dca6a31658f1ef0