TESTS: Minor Adsd test renaming

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
TESTS: Reorganized and cleaned Adsd tests

A few loops could be factorized, minor style fixes also.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
TESTS: In Adsd tests, modified an existing test to show issue

The too long decay (#60), resulting in a discontinuity in the envelop,
is catched by this line.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
TESTS: Added a test in Adsd for envelop regularity

This will help catching any audio click due to an irregular modulating
signal.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
MODULATORS: Fixed an imprecision in Adsd internal accumulator

This was leading to timings issues, especially the too long decay.
Fixed #60.

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