gmskframe: adding method to receive and synchronize preamble
gmskframe: adding method to receive and synchronize preamble

  * still needs a lot of work
  * saved samples don't match known p/n sequence
  * probably due to sample timing
  * delay of one sample due to instantaneous frequency estimate

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