Use fuse types in cython for platform compatibility

[AdrienCorenflos]

See https://cython.readthedocs.io/en/latest/src/userguide/fusedtypes.html

That is if main contributors want to stick to cython altogether.

[rflamary]

This would indeed be nice for emd_1d at least.

For the emd solver this might also actually help because the LEMON solver uses templates so we could possibly handle several types but would be much more complicated.