Changed semantics of AUTHENTICATION_WIN_LOG environment variable recognized by client library to accept the following values which are levels of logging done during Windows authentication handshake:
      
  0 - no logging
  1 - log only error messages
  2 - additionally log warnings
  3 - additionally log info notes
  4 - also log debug messages
      
Setting it to 'on', 'yes' or 'true' will request log level 2 and setting it to 'debug' or 'dbug' will request log level 4.