firfarrow/example: cleaning up example somewhat
firfarrow/example: cleaning up example somewhat

  * using new iirfilt_rrrf_create_lowpass() for signal input
  * moving input signal generation inside main loop
  * general code clean-up

jgaeddert/liquid-dsp,wangning223/liquid-dsp,JayKickliter/liquid-dsp,jgaeddert/liquid-dsp,manuts/liquid-dsp,JayKickliter/liquid-dsp,andrepuschmann/liquid-dsp,biotrump/liquid-dsp,andrepuschmann/liquid-dsp,jgaeddert/liquid-dsp,biotrump/liquid-dsp,jgaeddert/liquid-dsp,cjcliffe/liquid-dsp,JayKickliter/liquid-dsp,andrepuschmann/liquid-dsp,wangning223/liquid-dsp,wangning223/liquid-dsp,cjcliffe/liquid-dsp,cjcliffe/liquid-dsp,biotrump/liquid-dsp,manuts/liquid-dsp,cjcliffe/liquid-dsp,manuts/liquid-dsp,andrepuschmann/liquid-dsp,biotrump/liquid-dsp,manuts/liquid-dsp,wangning223/liquid-dsp,JayKickliter/liquid-dsp,wangning223/liquid-dsp,manuts/liquid-dsp,andrepuschmann/liquid-dsp,cjcliffe/liquid-dsp,jgaeddert/liquid-dsp,JayKickliter/liquid-dsp,biotrump/liquid-dsp