Added configurable script for filrunout form configuration.h

Marlin/Configuration.h

                                  // In RAMPS uses servo pin 2. Can be changed in pins file. For other boards pin definition should be made.
                                  // It is assumed that when logic high = filament available
                                  //                    when logic  low = filament ran out
-//const bool FIL_RUNOUT_INVERTING = true;  // Should be uncommented and true or false should assigned
-//#define ENDSTOPPULLUP_FIL_RUNOUT // Uncomment to use internal pullup for filament runout pins if the sensor is defined.
+#ifdef FILAMENT_RUNOUT_SENSOR
+  const bool FIL_RUNOUT_INVERTING = true;  // Should be uncommented and true or false should assigned
+  #define ENDSTOPPULLUP_FIL_RUNOUT // Uncomment to use internal pullup for filament runout pins if the sensor is defined.
+  #define FILAMENT_RUNOUT_SCRIPT "M600"
+#endif 
 
 //===========================================================================
 //============================ Mesh Bed Leveling ============================

Marlin/Marlin_main.cpp

   void filrunout() {
     if (!filrunoutEnqueued) {
       filrunoutEnqueued = true;
-      enqueuecommand("M600");
+      enqueuecommands_P(PSTR(FILAMENT_RUNOUT_SCRIPT));
+      st_synchronize();
     }
   }
-
 #endif
 
 void Stop() {