[GHC] #10064: Add support for "foo"## literals to MagicHash

[GHC]

#10064: Add support for "foo"## literals to MagicHash
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        Reporter:  chadaustin        |                   Owner:
            Type:  feature request   |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.8.4
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Comment (by chadaustin):

 Hi!  I don't think it's exactly the same as #5218 since I don't
 specifically need ByteStrings here, just a quick Int#, Addr# pair.  But
 #5218 could definitely be implemented on top of a mechanism that desugars
 to this (e.g. unpackCStringLen "my literal"##).

 If you'd like to merge the bugs, that's fine with me, as long as there's a
 way to get at some machinery to generate string length Int#s at compile
 time.  :)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10064#comment:3>
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