ssl: add msg_callback

[Thiébaud Weksteen]

Hi python-list,

I wrote a patch for Python 3.2.3 to expose the function
SSL_CTX_set_msg_callback in the module _ssl.

I was actually surprise this function was not already in the
standard library as it is really handy:
"SSL_CTX_set_msg_callback() or SSL_set_msg_callback() can be used
to define a message callback function cb for observing all SSL/TLS
protocol messages (such as handshake messages) that are received or
sent."

Here is the patch:
https://github.com/tweksteen/abrupt-usecase/blob/master/python-ssl-3.2.3.patch

Let me know your opinion on that. Does it worth being included?

Thiébaud