Stop F2Py from using the deprecated numpy API 

The f2py C code currently uses the pre 1.7 deprecated API, which causes lots of spurious warning messages when compiling Fortran extension modules with f2py (see #2639).

This pull request removes almost all of this, except for the `swap_arrays` and `dump_attrs` functions in fortranobject.c, which now cast the `PyArrayObject*` to `PyArrayObject_fields*`