Resolve "New nfft versions incompatible with octopus 12"

Closes #654 (closed)

From the discussion at https://github.com/pyNFFT/pyNFFT/issues/56, I understand that nfft3util.h is no longer included in newer versions of nfft(>3.3.2)(see https://github.com/NFFT/nfft/commit/9f91543bbc7271d1a8cc9c21cfc87287f921bdfe), the octopus configure script test with a code that includes "nfft3util.h" Thus the configure script must be updated.