* pnfft: new package
* Convert some packages with overridden install from AutotoolsPackage to Package
* pnfft: fix URL
* Switch FFTW-derived packages back to AutotoolsPackage
* Disable unneeded build phases in FFTW and derived packages
* Separate build phases for FFTW and derived packages
* Fix broken merge
* fftw: pfft_patches for 3.3.6
* fftw: address @adamjstewart’s review comments