+ comment some unclear fields of struct mansession;

+ let some commands (Challenge, Login) be processed even if
  already authenticated, as it doesn't harm and prevents some
  incorrect error messages

+ remove custom code for Logoff - the existing handler was ok.

Some indentation fixes may be necessary



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@45219 65c4cc65-6c06-0410-ace0-fbb531ad65f3