Changes to ghc

Changes to ghc:
commit 88d85aa65ea15d984bf207f82d99928eda0b6c26
Author: Herbert Valerio Riedel <hvr@gnu.org>
Date:   Sat Jun 28 20:23:48 2014 +0200

    Add BUILD_DPH variable to GHC build-system

    Now that the `libraries/dph` submodule is checked out always we need
    a different way to disable building DPH to save compile-time while
    developing GHC.

    This commit adds a new YES/NO Make variable `BUILD_DPH` that can be used
    inside mk/build.mk to control whether to build libraries/dph or not.
    The default setting is `BUILD_DPH=YES` (via `mk/config.mk.in`).

    This also changes `validate`'s flag `--no-dph` to explicitly disable DPH
    for the current validation run.

    Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>

    Test Plan: successful validates with `--fast --no-dph`

    Differential Revision: https://phabricator.haskell.org/D31