Testing safe renegotiation is relatively complex, here is a summary of

what we test and what how we believe it should work.

srn0.c:

 This tests that the safe renegotiation extension is negotiated

 properly by default on initial connections and on rehandshaked

 connections.  Consequently, it also verifies that rehandshaked

 connections work with the extension enabled.

srn4.c:

 This tests that clients without support for safe renegotiation is

 able to handshake properly against a default GnuTLS server, but

 that rehandshake will be refused by the server.

srn5.c:

 This tests that clients with support for safe renegotiation is able

 to handshake properly against a server with no support for safe

 renegotiation, but that the client will not be able to complete a

 rehandshake.