Add AudioNoInterrupts() and AudioInterrupts()

Audio.h

@@ -1,5 +1,20 @@
 #include "AudioStream.h"
 
+
+// When changing multiple audio object settings that must update at
+// the same time, these functions allow the audio library interrupt
+// to be disabled.  For example, you may wish to begin playing a note
+// in response to reading an analog sensor.  If you have "velocity"
+// information, you might start the sample playing and also adjust
+// the gain of a mixer channel.  Use AudioNoInterrupts() first, then
+// make both changes to the 2 separate objects.  Then allow the audio
+// library to update with AudioInterrupts().  Both changes will happen
+// at the same time, because AudioNoInterrupts() prevents any updates
+// while you make changes.
+#define AudioNoInterrupts() (NVIC_DISABLE_IRQ(IRQ_SOFTWARE))
+#define AudioInterrupts()   (NVIC_ENABLE_IRQ(IRQ_SOFTWARE))
+
+
 // waveforms.c
 extern "C" {
 extern const int16_t AudioWaveformSine[257];