Fix warnings about volatile being discarded

Author: facchinm

cores/arduino/WInterrupts.c

@@ -74,7 +74,7 @@ void attachInterrupt(uint8_t pin, void (*userFunc)(void), PinStatus mode) {
 
     /* Get pointer to correct pin control register */
     PORT_t *port = digitalPinToPortStruct(pin);
-    uint8_t* pin_ctrl_reg = getPINnCTRLregister(port, bit_pos);
+    volatile uint8_t* pin_ctrl_reg = getPINnCTRLregister(port, bit_pos);
 
     /* Clear any previous setting */
     *pin_ctrl_reg &= ~(PORT_ISC_gm);
@@ -97,7 +97,7 @@ void detachInterrupt(uint8_t pin) {
 
     /* Get pointer to correct pin control register */
     PORT_t *port = digitalPinToPortStruct(pin);
-    uint8_t* pin_ctrl_reg = getPINnCTRLregister(port, bit_pos);
+    volatile uint8_t* pin_ctrl_reg = getPINnCTRLregister(port, bit_pos);
 
     /* Clear ISC setting */
     *pin_ctrl_reg &= ~(PORT_ISC_gm);

cores/arduino/wiring_digital.c

@@ -48,7 +48,7 @@ void pinMode(uint8_t pin, PinMode mode)
 
 		uint8_t bit_pos = digitalPinToBitPosition(pin);
 		/* Calculate where pin control register is */
-		uint8_t* pin_ctrl_reg = getPINnCTRLregister(port, bit_pos);
+		volatile uint8_t* pin_ctrl_reg = getPINnCTRLregister(port, bit_pos);
 
 		/* Save state */
 		uint8_t status = SREG;
@@ -170,7 +170,7 @@ void digitalWrite(uint8_t pin, PinStatus val)
 		uint8_t bit_pos = digitalPinToBitPosition(pin);
 
 		/* Calculate where pin control register is */
-		uint8_t* pin_ctrl_reg = getPINnCTRLregister(port, bit_pos);
+		volatile uint8_t* pin_ctrl_reg = getPINnCTRLregister(port, bit_pos);
 
 		/* Save system status and disable interrupts */
 		uint8_t status = SREG;