Minor updates, improvements, and bug fixes.

- Allowed status_message function to be called by others. This is to
centralize all feedback into protocol.c.

- Fixed a bug where line number words 'N' were causing the parser to
error out.

- Allowed homing routine feed rates to move slower than the
MINIMUM_STEP_RATE parameter in config.h.

- Homing performs idle lock at the end of the routine.

- Stepper idle lock time will now not disable the steppers when the
value is set at 255. This is accomodate users who prefer to keep their
axes enabled at all times.

- Moved some defines around to where they need to be.

stepper.c

@@ -112,9 +112,11 @@ void st_go_idle()
   TIMSK1 &= ~(1<<OCIE1A); 
   // Force stepper dwell to lock axes for a defined amount of time to ensure the axes come to a complete
   // stop and not drift from residual inertial forces at the end of the last movement.
-  delay_ms(settings.stepper_idle_lock_time);   
+  delay_ms(settings.stepper_idle_lock_time);
   // Disable steppers by setting stepper disable
-  STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
+  if (settings.stepper_idle_lock_time != 0xff) {
+    STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT);
+  }
 }
 
 // This function determines an acceleration velocity change every CYCLES_PER_ACCELERATION_TICK by