Review 19960

C. Thomas Tyler
The Ultimate Perforce Login Script.

Enhanced p4login v3.1.0:
* If on a replica/edge server, logs in replication service users.
* Uses 'p4 login -a' for non-service type accounts, and 'p4 login 'for
  service type accounts.
* Accounts for auth.id, and behaves appropriately whether auth.id is set
  or not, e.g. doing an extra 'p4 login' as needed if auth.id isn't set.
* Logs in external automaiton users,  e.g. trigger or broker filter script
  users, if defined by the SDP_AUTOMATION_USERS setting in
  /p4/common/config/p4_<instance>.vars.
* Fixed bug where it broke if p4_vars wasn't sourced.  It now sources p4_vars.
* Logs whether actual 'p4 login' commands were needed and the number of logins
  done, along with other cosmetic logging enhancements.
* Added Version identifier.
Tip: Use n and p to cycle through the changes.