SCRIPTS: Updated Adsd script with last changes to C implementation

A few fixes were made to the C version, they're reported here.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
SYNTH: Fixed Vca missing the trigger ability!

The ability to trigger on/off the envelop has been forgotten in the last
edit, here it is fixed.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
MODUALTORS: Added a section getter for all envelop generators and Vca

This is very useful in tests, might find an utility also later
in the actual synth. There is almost no downside (minor code size growth).

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
COMMON: In math, added a function for filling a Sample with a generator

This is more functional-oriented and make some tests more elegant, so it
has been exposed in tests.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
TESTS: Added a test for Vca

This is a simple range test.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
TESTS: Added a test for modulated signal timings in Vca

This shows issue #58: the current Vca does not work with
per-sample processing.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
SYNTH: Fixed per-sample processing in Vca

This is still a bit sketchy, due to the fact that an ugly explicit
downcast has to be done.
When optimizing, the envelop generator will be templated since it is fixed
at compile-time: this will allow a better solution.
See #61

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