Individual extruder flow rate

Extension of M221, Tune menu

Marlin/ultralcd.cpp

@@ -414,6 +414,13 @@ static void lcd_tune_menu()
 #endif
     MENU_ITEM_EDIT(int3, MSG_FAN_SPEED, &fanSpeed, 0, 255);
     MENU_ITEM_EDIT(int3, MSG_FLOW, &extrudemultiply, 10, 999);
+    MENU_ITEM_EDIT(int3, MSG_FLOW0, &extruder_multiply[0], 10, 999);
+#if TEMP_SENSOR_1 != 0
+    MENU_ITEM_EDIT(int3, MSG_FLOW1, &extruder_multiply[1], 10, 999);
+#endif
+#if TEMP_SENSOR_2 != 0
+    MENU_ITEM_EDIT(int3, MSG_FLOW2, &extruder_multiply[2], 10, 999);
+#endif
 
 #ifdef BABYSTEPPING
     #ifdef BABYSTEP_XY