[GHC] #9265: Extend PackageId to include version dependency information

[GHC]

#9265: Extend PackageId to include version dependency information
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        Reporter:  ezyang            |            Owner:  ezyang
            Type:  feature request   |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Package system    |          Version:  7.9
      Resolution:                    |         Keywords:  backpack
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by ezyang):

 No, C libraries won't get mangled; they'll be shared (in much the same way
 if two different Haskell packages ask for the same C library, they'll get
 the same one linked in.)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9265#comment:3>
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