Changes to integer-gmp

Changes to integer-gmp:
commit e94799c9d5e15fc03bc226197b00b1d4b1189945
Author: Herbert Valerio Riedel <hvr@gnu.org>
Date:   Tue Nov 5 12:08:00 2013 +0100

    Add primitives to write/read Integers to/from bytearrays

    This adds the following new (internal) primitives

    {{{#!hs
    sizeInBaseInteger :: Integer -> Int# -> Word#

    exportInteger :: Integer -> MutableByteArray# s -> Word# -> Int#
                     -> State# s -> (# State# s, Word# #)

    importInteger :: ByteArray# -> Word# -> Word# -> Int# -> Integer
    }}}

    The import/export primitives support selecting most/least significant
    byte first order as well as using an offset into the byte-arrays.

    See Haddock comments for more details.

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