New demodulation parts in RCG
RCG needs new simulink demodulation parts, useful for fast ADC and low noise ADC IOPs.
These parts will be based on Daniel's code here: https://redoubt.ligo-wa.caltech.edu/svn/slowcontrols/trunk/EPICS/Utilities/BiquadAVX
RCG will pick best available version of Demod for build, possibly based on flag or native compiler.
8-input and 16-input parts of single and multiple frequencies.