Changes to ghc(3)

Changes to ghc:
commit 17c955402871862dea5021e0b83b0949da5e51e7
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Tue Apr 8 09:43:13 2014 +0100

    Improve documentation of GeneralisedNewtypeDeriving

commit 4dc9f9869bfc82fdb8bd61864859007873ebcc27
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Tue Apr 8 09:42:51 2014 +0100

    Zonk the existential type variables in tcPatSynDecl

    This was just an omission, which showed up as Trac #8966

commit cbe59d89f2f1cc41147fabb4a4c58126152bef7f
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Tue Apr 8 09:41:20 2014 +0100

    Improve tracing slightly