Fix digitalRead alias warning

Author: earlephilhower

cores/esp8266/core_esp8266_wiring_digital.cpp

@@ -252,7 +252,7 @@ extern void initPins() {
 
 extern void pinMode(uint8_t pin, uint8_t mode) __attribute__ ((weak, alias("__pinMode")));
 extern void digitalWrite(uint8_t pin, uint8_t val) __attribute__ ((weak, alias("__digitalWrite")));
-extern int digitalRead(uint8_t pin) __attribute__ ((weak, alias("__digitalRead")));
+extern int digitalRead(uint8_t pin) __attribute__ ((weak, alias("__digitalRead"), nothrow));
 extern void attachInterrupt(uint8_t pin, voidFuncPtr handler, int mode) __attribute__ ((weak, alias("__attachInterrupt")));
 extern void attachInterruptArg(uint8_t pin, voidFuncPtrArg handler, void* arg, int mode) __attribute__((weak, alias("__attachInterruptArg")));
 extern void detachInterrupt(uint8_t pin) __attribute__ ((weak, alias("__detachInterrupt")));