#35 Updates AM & NBFM decoders to use Adaptive Squelch, a power squelch that includes an adaptive noise floor monitor. Implements vectorized magnitude operations for AM & FM decoders. Adds talkgroup assignment and squelch controls to AM channel configuration editor. Implements new AM gain control that attempts to normalize audio gain quickly at beginning of call/transmission and maintains that gain across lifecycle of the call and resets the gain for the next call. (#1540)

Notes on usage:
- When using either AM or FM squelch control use either the Heterodyne channelizer or if using the Polyphase channelizer, avoid using trunk tracking decoders like DMR or P25 or set the squelch threshold high enough to avoid changes in noise floor from polyphase channelizer where it can vary between using the one channel or the two-channel combined channel sources.

Co-authored-by: Dennis Sheirer <dsheirer@github.com>

src/main/java/io/github/dsheirer/audio/AudioModule.java

@@ -141,11 +141,16 @@ public class AudioModule extends AbstractAudioModule implements ISquelchStateLis
         @Override
         public void receive(SquelchStateEvent event)
         {
-            mSquelchState = event.getSquelchState();
+            SquelchState squelchState = event.getSquelchState();
 
-            if(mSquelchState == SquelchState.SQUELCH)
+            if(mSquelchState != squelchState)
             {
-                closeAudioSegment();
+                mSquelchState = squelchState;
+
+                if(mSquelchState == SquelchState.SQUELCH)
+                {
+                    closeAudioSegment();
+                }
             }
         }
     }