Some code in the demod rotation calcs was compiled with the assumption that %rax was preserved across a call to sincos.
This is not the case.  Now sincos saves %rax on the stack.

Also some fixes to comments in demod parts.

These parts demodulate a single signal against multiple frequencies.

Also, some bugs fixed in demod parts.

16-input dmodulation_decimation library part now works in non-vectorized and avx2 modes.  Other modes cause a kernel panic.
models have a new parameter, "vectorization" that can be set to avx512, avx2, sse3 or none (default).