Rename filament runout items

Marlin/Marlin.h

 void Stop();
 
 #if ENABLED(FILAMENT_RUNOUT_SENSOR)
-  void filrunout();
+  void handle_filament_runout();
 #endif
 
 /**

Marlin/Marlin_main.cpp

 #endif
 
 #if ENABLED(FILAMENT_RUNOUT_SENSOR)
-  static bool filrunoutEnqueued = false;
+  static bool filament_ran_out = false;
 #endif
 
 static bool send_ok[BUFSIZE];
     #endif
 
     #if ENABLED(FILAMENT_RUNOUT_SENSOR)
-      filrunoutEnqueued = false;
+      filament_ran_out = false;
     #endif
 
   }
 
   #if HAS_FILRUNOUT
     if (IS_SD_PRINTING && !(READ(FILRUNOUT_PIN) ^ FIL_RUNOUT_INVERTING))
-      filrunout();
+      handle_filament_runout();
   #endif
 
   if (commands_in_queue < BUFSIZE) get_available_commands();
 
 #if ENABLED(FILAMENT_RUNOUT_SENSOR)
 
-  void filrunout() {
-    if (!filrunoutEnqueued) {
-      filrunoutEnqueued = true;
+  void handle_filament_runout() {
+    if (!filament_ran_out) {
+      filament_ran_out = true;
       enqueue_and_echo_commands_P(PSTR(FILAMENT_RUNOUT_SCRIPT));
       st_synchronize();
     }