Fix sinoscfb phase

[capital-G]

The docs state that sinoscfb has a modulatable phase

sapf> `sinoscfb help
@zzz (freq phase feedback --> out) sine wave oscillator with self feedback phase modulation

but when spawning a sinoscfb with a modulatable phase this fails

sapf> 0.0 100.0 0.0 sinosc 0.0 sinoscfb play
error: wrong type for  sinoscfb : phase .  expected Float. got ZList.
backtrace: opCallImmediate {Prim, sinoscfb}
error: wrong type

this PR makes the phase modulatable by adding an offset to the internal phase so this works as expected

sapf> 0.0 100.0 0.0 sinosc 0.0 sinoscfb play
start output unit OK