39 [WIP] - restructured the polyphase filter process. Previous version

was not computationally feasible with my 3rd Gen i7 processor running
and airspy at 10 MHz.  Restructured the polyphase channelizer to use
vector iteration structures that the JDK 9 JIT compiler can translate
into SIMD instructions.  Separated the IFFT processing from the filter
process so that they can be executed on separate threads and this allows
the processing to occur real time.

P25 C4FM decoding at 25 kHz channel sample rate using an airspy
10MHz sample stream seems to be working nicely with ~25% CPU usage and
~300 to 500 MB memory usage.  Incremental (parallel) channel decoding
should have a minimal increase in CPU loading since all of the 12.5 kHz
channels are available in the polyphase channelizer and the only
additional workload is the decoding of the 25 kHz sample stream.

There is still an issue with stopping channels and the channelizer keeps
 processing, and occasionally when starting traffic channels something
 deadlocks and causes out of memory.

src/main/java/io/github/dsheirer/sample/OverflowableTransferQueue.java

@@ -115,6 +115,23 @@ public class OverflowableTransferQueue<E>
         return drainCount;
     }
 
+    /**
+     * Retrieves elements from the queue into the collection up to the maximum number of elements specified
+     */
+    public int drainTo(Collection<? super E> collection)
+    {
+        int drainCount = mQueue.drainTo(collection);
+
+        int size = mCounter.addAndGet(-drainCount);
+
+        if(mOverflow.get() && size <= mResetThreshold)
+        {
+            setOverflow(false);
+        }
+
+        return drainCount;
+    }
+
     /**
      * Sets a listener to receive overflow state change events.
      */