Add EEPROM_SIZE to mega boards.

Author: James Foster

SampleProjects/TestSomething/test/eeprom.cpp

@@ -9,13 +9,6 @@ unittest(length)
   assertEqual(EEPROM_SIZE, EEPROM.length());
 }
 
-#else
-
-unittest(eeprom)
-{
-  assertTrue(true);
-}
-
 #endif
 
 unittest_main()

cpp/arduino/avr/iomxx0_1.h

@@ -351,6 +351,17 @@
    Last two letters:   EEAR address.  */
 #define __EEPROM_REG_LOCATIONS__ 1F2021
 
+/* According to https://ww1.microchip.com/downloads/en/devicedoc/atmel-2549-8-bit-avr-microcontroller-atmega640-1280-1281-2560-2561_datasheet.pdf,
+ * the Atmel ATmega640/V-1280/V-1281/V-2560/V-2561/V microcontrollers each have 
+ * 4Kbytes of EEPROM and since this file is included from things that seem
+ * to match that description, it would be helpful to know that EEPROM is 
+ * available and know its size. This macro is defined for many other models,
+ * so we will add it here.
+ * 
+ * See https://github.com/Arduino-CI/arduino_ci/issues/166#issuecomment-703904394.
+ */
+#define EEPROM_SIZE     (4096)
+
 #define GTCCR   _SFR_IO8(0x23)
 #define TSM     7
 #define PSRASY  1