Better picking CPP


git-svn-id: https://smlnj-gforge.cs.uchicago.edu/svn/manticore/trunk@5780 ac4fbcad-d21d-0410-b760-c7b1d3380187
fixed typo in configure.ac, but a new mysterious cpp problem remains on OS X

git-svn-id: https://smlnj-gforge.cs.uchicago.edu/svn/manticore/trunk@5783 ac4fbcad-d21d-0410-b760-c7b1d3380187