First parts 2nd extruder

Marlin/planner.cpp

@@ -81,6 +81,8 @@ float max_z_jerk;
 float mintravelfeedrate;
 unsigned long axis_steps_per_sqr_second[NUM_AXIS];
 
+uint8_t active_extruder = 0;
+
 // The current position of the tool in absolute steps
 long position[4];   //rescaled from extern when axis_steps_per_unit are changed by gcode
 static float previous_speed[4]; // Speed of previous path line segment