Log Message:
math/fftw and dependents: merge math/fftwf backin and add MPI and OpenMP

This yields one common package to provide libfftw3 (double) and libfftw3f
(single) by default and optionally the Fortran bindings as well as
OpenMP and MPI variants, and those with long double or quad precision.

This changes all packages depending on fftwf in the same commit to minimize
the time of inconsistency. Soon, math/fftwf will disappear.