fixed a small problem when mac plugins are opened and closed quickly by the host

src/juce_appframework/audio/processors/juce_AudioProcessor.h

@@ -276,6 +276,10 @@ public:
         filter will return an empty buffer, but won't block the audio thread like it would
         do if you use the getCallbackLock() critical section to synchronise access.
 
+        If you're going to use this, your processBlock() method must call isSuspended() and
+        check whether it's suspended or not. If it is, then it should skip doing any real
+        processing, either emitting silence or passing the input through unchanged.
+
         @see getCallbackLock
     */
     void suspendProcessing (const bool shouldBeSuspended);