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, and behaves appropriately whether is set
  or not, e.g. doing an extra 'p4 login' as needed if 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
* 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.
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