Allow AudioInputAnalog to use different pins

input_adc.cpp

 DMAChannel AudioInputAnalog::dma(false);
 
 
-AudioInputAnalog::AudioInputAnalog() : AudioStream(0, NULL)
+AudioInputAnalog::AudioInputAnalog(uint8_t pin) : AudioStream(0, NULL)
 {
-	unsigned int pin = A2;
 	uint32_t i, sum=0;
 
 	// Configure the ADC and run at least one software-triggered

input_adc.h

 class AudioInputAnalog : public AudioStream
 {
 public:
-        AudioInputAnalog();
+        AudioInputAnalog(uint8_t pin);
+        AudioInputAnalog() : AudioStream(0, NULL) { AudioInputAnalog(A2); }
         virtual void update(void);
         friend void dma_ch9_isr(void);
 private: