Changes to ghc(3)

Changes to ghc:
commit af6746fb6b5adb5ba5be6e0f647c4ebe767ce084
Author: Simon Marlow <marlowsd@gmail.com>
Date:   Thu Feb 27 14:07:29 2014 +0000

    Add hs_thread_done() (#8124)

    See documentation for details.

commit 68c0d8689dd93cb0ce74a288e82f2ed997c31acc
Author: Simon Marlow <marlowsd@gmail.com>
Date:   Thu Feb 27 12:37:32 2014 +0000

    fix comment on allocate() (#8254)

commit b1ddec1e6d4695d71d38b59db26829d71ad784e1
Author: Simon Marlow <marlowsd@gmail.com>
Date:   Thu Feb 27 09:41:19 2014 +0000

    Fix a bug in codegen for non-updatable selector thunks (#8817)

    To evaluate most non-updatable thunks, we can jump directly to the
    entry code if we know what it is.  But not for a selector thunk: these
    might be updated by the garbage collector, so we have to enter the
    closure with an indirect jump through its info pointer.