BREAKING CHANGE: If song uses a speed unit, SU_LENGTH_IN_SAMPLES,
SU_BUFFER_LENGTH and SU_SYNCBUFFER_LENGTH won't be defined in the
generated header file, as we cannot know their exact values during
compile time without rendering the entire song. When using a speed
unit, the user has to take responsibility of allocating large enough
buffers.
Closes#241
ConstructPatterns was never used except during compilation, so it
makes sense to have it closer where it is used. We could consider
making it even private function, as the pattern table construction
is quite specific to how compiler compiles and probably not that
reusable elsewhere.
There is a new "sync" opcode that saves the top-most signal every 256 samples to the new "syncBuffer" output. Additionally, you can enable saving the current fractional row as sync[0], avoiding calculating the beat in the shader, but also calculating the beat correctly when the beat is modulated.