let the user know that EEPROM is being erased

it takes about 10-12 seconds, so its nice to know whats going on

git-svn-id: https://arducopter.googlecode.com/svn/trunk@3250 f9c3cf11-9bcb-44bc-f272-b75c42450872

ArduCopterMega/system.pde

@@ -115,6 +115,8 @@ static void init_ardupilot()
 		*/
 
 		// erase all parameters
+		Serial.printf_P(PSTR("Firmware change: erasing EEPROM...\n"));
+		delay(100); // wait for serial send
 		AP_Var::erase_all();
 
 		// save the new format version