Update and bugfix for LV2 support

[jpcima]

I have updated foo-yc20 to support the latest faust 0.9.x and modern LV2.
The LV2 used extensions which are long deprecated and not supported in Jalv.
I believe this should fix issues #6 and #7.

This is how the implementation is affected by changes.

• I have generated the faust code without the architecture file minimal.cpp. Under the new faust it produced a dummy main() function which is in conflict with the code of foo-yc20.
• The precalculated oscillators. LV2 did not initialize them, crashing the instrument on the first run.
  I converted these tables from global to one per instance. I make the oscillator pointer thread-local to keep the code like it is, but protect if there are concurrent runs. This thread-local may introduce a small runtime cost, which I have not measured.
• UI2 does not refresh the display after there are interactions. I fix it by refreshing the draw area in mouse event handlers.

[jpcima]

update: I have found how to keep the oscillator table pointer in the DSP object.
I have eliminated the requirement for thread-local.

[sampov2]

Thanks for the pull request. Unfortunately I don't have a development environment where I would be able to test this. @trebmuh - have you been able to test these fixes? My main question is that did we lose any functionality? For example, is the MIDI support still there?

[jpcima]

I have tested LV2 and standalone with Midi under Linux+Jack. There is no change in relation with Jack Midi, however LV2 has needed a transition from the old Event extension to Atom.
However I realize just now there is also a VST version and I have not tried it. It must not be difficult, I will give it a try shortly and add changes if necessary.
I can try Windows and Linux unfortunately I do not have access to Mac.

[sampov2]

Thanks. Let me know if you're successful in testing the VST support.

[jpcima]

I tested the VST in 2 configurations: dssi-vst (Wine) and VSTHost for Windows.
It took the same changes than LV2 to avoid a crash in the process routine.
It takes a bit of effort to build in a recent mingw. I just include relevant changes to not overload the commit.

I could add some maintainance needed in other commits. (mingw has evolved a lot but much of the foo-yc20 code is a few years old).

[sampov2]

Looks good. Thanks for the work!

[sampov2]

As for the mingw stuff, it would be great if there was an online build service that offered mingw support that we could use to produce the DLL's. Do you happen to know if there are any available?

[jpcima]

I am afraid not, I am not familiar with such services.
The simplest route to setting up a mingw build environment with libraries must be msys2. Personally I use a cross-compilation toolchain from Linux.

[sampov2]

I found a docker project that has containers with crosscompilers: https://github.com/dockcross/dockcross . This could be very good option as containers could offer a stable compilation environment to perform repeatable builds.