WIP: fix build issue with g77 for linalg.interpolative.

Type of errors that this fixes::

    Argument #5 (named `ifac') of `zfftb1' is one type at (2) but is some
    other type at (1) [info -f g77 M GLOBALS]

Warning shows up with gfortran as::

    Warning: Type mismatch in argument 'ifac' at (1); passed REAL(8) to INTEGER(4)

Issue can also be fixed by compiling with -fno-globals, but passing
Fortran flags with distutils is quite painful.