Fix unknown symbol base_ControlziExceptionziBase_patError_info by helping GHC generate smarter core.

See the comments with toInt#, but the key point is
that we want (fromInteger 1)::Int to yield (I# 1)!

A missing | meant that the build broke on machines that don't have
libgmp available.

Ian Lynagh <igloo@earth.li>**20100118191831

We were building GMP even if we didn't need to.

rolling back:

Sat Nov 21 16:43:13 EST 2009  Ben.Lippmeier@anu.edu.au
  * Windows DLLs: Tag imported gmp symbols with the package they're from.

    M ./cbits/gmp-wrappers.cmm -20 +20

- Needed to get arch-dependent options, eg, on Snow Leopard