saugns v0.3.7c. Rearrange code. Fix hang with -r 1. Reduce design difference with 2020-06 "mgensys" a bit further; split "generator" pre-allocation code into prealloc (like a simpler runalloc), and merge voicegraph into prealloc. Also rename generator to interp. Fix hang with the useless, yet allowed, sample rate of 1 Hz due to 0 samples being generated per "run" call, and time thus never advancing for the interpreter. Simply end when 0 samples are filled in the player code.