Fix issues pointed out by nickm.

Fix issues pointed out by nickm.

- Rename tor_tls_got_server_hello() to tor_tls_got_client_hello().
- Replaced some aggressive asserts with LD_BUG logging.

  They were the innocent "I believe I understand how these callbacks
  work, and this assert proves it" type of callbacks, and not the "If
  this statement is not true, computer is exploding." type of
  callbacks.
- Added a changes file.