Update nfft to 3.5.1 and add octave binding. Resolves T9116.

A changelog from 3.4.x can be found at https://github.com/NFFT/nfft/blob/develop/ChangeLog

• python binding:
  • pip install nfft-cffi
  • # extract tests/test_nfft.py from nfft-cffi tarball
  • nosetests test_nfft.py
  • # all tests should pass
• octave binding:
  • octave
  • addpath('/usr/share/nfft/matlab/nfft/', '/usr/lib64')
  • simple_test