* Remove is_scram_verifier() function. It was unused.
* Fix sanitize_char() function, used in error messages on protocol
  violations, to print bytes >= 0x7F correctly.
* Change spelling of scram_MockSalt() function to be more consistent with
  the surroundings.
* Change a few more references to "server proof" to "server signature" that
  I missed in commit d981074c.