[GHC] #11015: Add note describing unit ids, unit keys, package ids, and package keys,

[GHC]

#11015: Add note describing unit ids, unit keys, package ids, and package keys,
-------------------------------------+-------------------------------------
        Reporter:  bgamari           |                Owner:  ezyang
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.11
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by bgamari):

 Has this happened by any chance?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11015#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler