This change makes it consistent with iOS.

This test will be replaced later with something better.

This does not yet implement the filter backends. It only does the data
retrieval and buffer management part of it.

The requirement for pointers to be aligned to MAL_SIMD_ALIGNMENT has
been dropped because it is adding too many complications to the
implementation.

The rationale for this is that it's just useless - just not do
resampling at all if you don't need to!

This commit also simplifies a few APIs with respect to how the
fractional component is handled.