STABLE14-more-cpp-fixes-20080701

STABLE14-more-cpp-fixes-20080701

LICENSE BSD

Use PATH_CPP instead of CPP everywhere and always redirect the output
instead of assuming that it will write to a file.  Hopefully this is the
least common denominator across all systems, although it still isn't
fully correct for systems that have no separate cpp binary.

(cherry picked from commit c733e2e07aeb0cc981d53d843a1ffb787f43ed64)