General code and functionality improvements. Moved more code out of the
OpenGL backend for portability. Implemented audio transitions.
Implemented basic transition animation curve settings.
The nodes now have more control over how their accelerated shaders/sample
functions are run, as well as how items are popped off the value tables.
This allows for various optimizations that we didn't have access to before.
As opposed to simply leaving all values in the table, nodes can now "take"
values that they use to free up memory (e.g. "taking" input buffers if they're
used to produce an output buffer).
This is a fairly large change, expect regressions.
itsmattkc