Copter: add LOG_FROM_STARTUP definition

Uncommenting this line in APM_Config.h will start logging as soon as the
board starts up instead of waiting for the vehicle to be armed

ArduCopter/APM_Config.h

@@ -44,6 +44,7 @@
 // other settings
 //#define THROTTLE_IN_DEADBAND   100                // redefine size of throttle deadband in pwm (0 ~ 1000)
 //#define LAND_REQUIRE_MIN_THROTTLE_TO_DISARM   DISABLED    // when set to DISABLED vehicle will disarm after landing (in LAND mode or RTL) even if pilot has not put throttle to zero
+//#define LOG_FROM_STARTUP                          // start logging as soon as the board starts up instead of waiting for the vehicle to be armed
 
 //#define HIL_MODE              HIL_MODE_SENSORS    // build for hardware-in-the-loop simulation
 

ArduCopter/system.pde

@@ -279,6 +279,10 @@ static void init_ardupilot()
 
 #if LOGGING_ENABLED == ENABLED
     Log_Write_Startup();
+  #ifdef LOG_FROM_STARTUP
+    // start dataflash
+    start_logging();
+  #endif
 #endif
 
     // we don't want writes to the serial port to cause us to pause