* This partially reverts "added support for C89/90 preprocessor" which only
  covered up an already bad situation.

Using the C preprocessor on Fortran sources does ultimately not work
since it doesn't know about Fortran-specific features like the _OPENMP
macro and is chronically likely to pick up the cpp belonging to
another compiler (e.g. to system gcc when compiling with xlf on Linux/ppc).

* The only user immediately destroyd the copy.

* Replace expensive function call with comparison.

* It's only in grib_api releases 1.12 and after.

* Also automatically find cfortran.h flag for as many platforms as we
  can test at the moment.