Added definitions for DAC0 in variants

Fix #126

Author: cmaglie

variants/arduino_zero/variant.h

@@ -96,13 +96,15 @@ extern "C"
 #define PIN_A3               (17ul)
 #define PIN_A4               (18ul)
 #define PIN_A5               (19ul)
-
-static const uint8_t A0  = PIN_A0 ;
-static const uint8_t A1  = PIN_A1 ;
-static const uint8_t A2  = PIN_A2 ;
-static const uint8_t A3  = PIN_A3 ;
-static const uint8_t A4  = PIN_A4 ;
-static const uint8_t A5  = PIN_A5 ;
+#define PIN_DAC0             (14ul)
+
+static const uint8_t A0  = PIN_A0;
+static const uint8_t A1  = PIN_A1;
+static const uint8_t A2  = PIN_A2;
+static const uint8_t A3  = PIN_A3;
+static const uint8_t A4  = PIN_A4;
+static const uint8_t A5  = PIN_A5;
+static const uint8_t DAC0 = PIN_DAC0;
 #define ADC_RESOLUTION		12
 
 // Other pins