Changes to ghc(4)

Changes to ghc:
commit 453a092e5f2b7abf35e7b0baa642658e0d545e9d
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Fri Oct 25 14:43:25 2013 +0100

    Untabify and remove trailing whitespace

    ... plus a couple of unused variables in TcSMonad

commit e55f516766c5a0ece06f2c36dc31601dcdeb97cd
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Fri Oct 25 14:36:37 2013 +0100

    Remove canSolve in favour of canRewrite

    There was no useful distinction; a simple refactoring.

commit 54717c8218cb27b1f1f56ba019c17494556f766c
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Fri Oct 25 14:35:37 2013 +0100

    Be more careful when iterating the constraint-simpifier loop (fixes Trac #8474)

    We were (uselessly) iterating the simplification loop an exponential
    number of times.  Lovely simple test case showed this up.

    See Note [Cutting off simpl_loop] in TcSimplify

commit 6e30aeae5b37636c221d5627e9a9649894075ce8
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Thu Oct 24 15:55:20 2013 +0100

    Add a tiny bit more tracing