TLSServer

- Added extra diagnostics for the gnutls calls.
s, c

- Enabled debug mode by default.  What else is this demo code for?
TLSServer

- Code cleanup.
TLSTransaction

- Now propagates trust from TLSServer to TLSTransaction.
- Properly instantiates _ca.
TLSServer

- Ådded verify_certificate method, instead of a static function, which gives
  it access to members needed in the verification.