pnfft: fix init_x_3d_adv

would always produce x > x_max
pnfft: tests: use pnfft_init_x_3d{,_adv}
pnfft: allow tests to be run from any directory
pnfft: add function for debug printing
pnfft: store fourier coefficients as R*
pnfft: Don't store f_hat as R, we only support c2r and c2c transforms
pnfft: store pfft input as R*
pfft input as R: fix rebase fail
pfft: add apr_real_3d for printing real 3d-arrays
pnfft: add apr_real_3d for printing real 3d-arrays
pnfft: simple test: for c2r
pnfft: add test to check c2r error
pnfft: add define for c2r transform
pnfft: C2R
pnfft: fixes
pnfft: pnfft_user_flags -> trafo_flag, no prefix for local_size_internal
pnfft: add missing c2r interface
pnfft: c2r: allocate enough storage for forw and back trafo
pnfft: test_adv_c2r: make local_M big enough for c2r
[WARNING] This branch will be rebased (enable debug)

at the moment, r2c/c2r transforms don't work yet,
but at least c2c transforms aren't broken