Use implicit CallStacks for ASSERT when available
Use implicit CallStacks for ASSERT when available

This aids with debugging, since all you have to do to get more
stack frames is add a constraint `(?callStack :: CallStack) =>`.

Old output:
```
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 8.1.20160107 for x86_64-unknown-linux):
        ASSERT failed!
  file compiler/types/TyCoRep.hs line 1800
  InScope []
  [Xuv :-> n_av5[sk]]
  []
```

New output:
```
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 8.1.20160107 for x86_64-unknown-linux):
        ASSERT failed!
  CallStack (from ImplicitParams):
  assertPprPanic, called at compiler/types/TyCoRep.hs:1800:95 in
ghc:TyCoRep
  InScope []
  [Xuv :-> n_av5[sk]]
  []
```

Test Plan:
harbormaster
manual testing

Reviewers: austin, gridaphobe, bgamari

Reviewed By: gridaphobe, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1751

nushio3/ghc,vTurbine/ghc,oldmanmike/ghc,sgillespie/ghc,gridaphobe/ghc,nushio3/ghc,ezyang/ghc,sdiehl/ghc,vikraman/ghc,mettekou/ghc,shlevy/ghc,snoyberg/ghc,mcschroeder/ghc,vikraman/ghc,shlevy/ghc,olsner/ghc,snoyberg/ghc,tjakway/ghcjvm,vTurbine/ghc,mettekou/ghc,sgillespie/ghc,nushio3/ghc,oldmanmike/ghc,olsner/ghc,snoyberg/ghc,vikraman/ghc,shlevy/ghc,tjakway/ghcjvm,mettekou/ghc,sdiehl/ghc,ezyang/ghc,nushio3/ghc,vikraman/ghc,ezyang/ghc,vTurbine/ghc,vTurbine/ghc,ezyang/ghc,mcschroeder/ghc,gridaphobe/ghc,mcschroeder/ghc,olsner/ghc,oldmanmike/ghc,sdiehl/ghc,shlevy/ghc,sdiehl/ghc,nushio3/ghc,tjakway/ghcjvm,snoyberg/ghc,vTurbine/ghc,ezyang/ghc,oldmanmike/ghc,gridaphobe/ghc,gridaphobe/ghc,olsner/ghc,ezyang/ghc,ezyang/ghc,olsner/ghc,shlevy/ghc,snoyberg/ghc,oldmanmike/ghc,mettekou/ghc,vikraman/ghc,nushio3/ghc,snoyberg/ghc,sgillespie/ghc,olsner/ghc,vTurbine/ghc,sdiehl/ghc,mettekou/ghc,gridaphobe/ghc,gridaphobe/ghc,sgillespie/ghc,shlevy/ghc,mcschroeder/ghc,sdiehl/ghc,tjakway/ghcjvm,oldmanmike/ghc,shlevy/ghc,vikraman/ghc,gridaphobe/ghc,vTurbine/ghc,mcschroeder/ghc,sgillespie/ghc,sdiehl/ghc,tjakway/ghcjvm,olsner/ghc,nushio3/ghc,mettekou/ghc,sgillespie/ghc,mcschroeder/ghc,oldmanmike/ghc,tjakway/ghcjvm,mettekou/ghc,vikraman/ghc,tjakway/ghcjvm,mcschroeder/ghc,sgillespie/ghc,snoyberg/ghc