[GHC] #13779: Add more signature suppression control for dumps

[GHC]

#13779: Add more signature suppression control for dumps
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.2.1-rc2
      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:                    |
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Comment (by dfeuer):

 I mostly want to be able to suppress them in function arguments. `\(x ::
 HUGE TYPE). ...`. Being able to suppress them in `let` bindings separately
 wouldn't be bad either.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13779#comment:3>
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