SYNTH: Using explicit float type everywhere for interpolation

Vectorized interpolation is not on the agenda.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
SYNTH: Minor code cleaning

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
SYNTH: Now using the Adapter output buffer

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
SYNTH: Added an output sampling frequency setter

This allows to dynamically change the output audio stream sampling
frequency.
In order to test it, the performance test has been doubled in two tests,
each one at a different sampling rate.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>