added EEPROM.update(address, val) method

EEPROM.update(address, val) is part of the official Arduino API.
See https://wiki-content.arduino.cc/en/Tutorial/LibraryExamples/EEPROMUpdate
for more information.

Author: ole00

libraries/EEPROM/src/EEPROM.h

@@ -45,7 +45,9 @@ class EEPROMClass {
   uint16_t length();
   bool commit();
   void end();
-
+  void update(int address, uint8_t val) {
+    if (read(address) != val) write(address, val);
+  }
   uint8_t *getDataPtr();
   uint16_t convert(bool clear, const char *EEPROMname = "eeprom", const char *nvsname = "eeprom");