AP_ADC_AnalogSource: fixed APM1 build

libraries/AP_ADC_AnalogSource/AP_ADC_AnalogSource.cpp

@@ -28,7 +28,6 @@ float AP_ADC_AnalogSource::voltage_average()
     return fullscale * 3.3 * 2.44140625e-4f;
 }
 
-
 void AP_ADC_AnalogSource::set_pin(uint8_t machtnichts) {
     /* it would be an error to call this
      * but for now we'll leave it a no-op. */

libraries/AP_ADC_AnalogSource/AP_ADC_AnalogSource.h

@@ -15,6 +15,7 @@ public:
     float           read_latest(void);
     void            set_pin(uint8_t);
     float	    voltage_average();
+    float	    voltage_latest() { return voltage_average(); }
     float	    voltage_average_ratiometric() { return voltage_average(); }
 
     // stop pins not implemented on ADC yet