message: AFC: Add AFC structure to BTNRH_WDRC_Types.h
diff: namespace BTNRH_WDRC {
  + // Here are the settings for the adaptive feedback cancelation
  + typedef struct {
  + int default_to_active; //enable AFC at startup? 1=active. 0=disabled.
  + int afl; //length (samples) of adaptive filter for modeling feedback path.
  + float mu; //mu, scale factor for how fast the adaptive filter adapts (bigger is faster)
  + float rho; //rho, smoothing factor for estimating audio envelope (bigger is a longer average)
  + float eps; //eps, when est the audio envelope, this is the min allowed level (avoids divide-by-zero)
  + } CHA_AFC;
  +
  // from CHAPRO cha_ff.h
  #define DSL_MXCH 32
  //class CHA_DSL {
  