PFFT, PNFFT: fix build with --disable-doc
P2NFFT: fix command line argument
incorporate PFFT bugfix
remove deprecated code
add Mathematica calls for parameter computation
P2NFFT: better name for precomputation function
P2NFFT: delete deprecated code, add timer for precomputation
2dp-P2NFFT: skip regularization for vanishing functions