Add bitToggle macro to complement bitSet etc

Port of arduino/ArduinoCore-avr@0c5aa78
Reference PR: arduino/ArduinoCore-avr#31

Author: jamadagni

Diff for: api/Common.h

@@ -64,6 +64,7 @@ typedef void (*voidFuncPtrParam)(void*);
 #define bitRead(value, bit) (((value) >> (bit)) & 0x01)
 #define bitSet(value, bit) ((value) |= (1UL << (bit)))
 #define bitClear(value, bit) ((value) &= ~(1UL << (bit)))
+#define bitToggle(value, bit) ((value) ^= (1UL << (bit)))
 #define bitWrite(value, bit, bitvalue) (bitvalue ? bitSet(value, bit) : bitClear(value, bit))
 
 #ifndef bit