add switch_hashtable_insert_destructor so you can insert a pointer into a hash with a custom destructor and use it in spandsp to fix a leak on reloadxml with the tone_descriptor tables and fix a bunch of random tiny leaks etc

src/mod/languages/mod_v8/mod_v8.cpp

@@ -872,6 +872,7 @@ SWITCH_MODULE_SHUTDOWN_FUNCTION(mod_v8_shutdown)
 	switch_mutex_destroy(globals.event_mutex);
 
 	switch_core_hash_destroy(&module_manager.load_hash);
+	switch_core_destroy_memory_pool(&module_manager.pool);
 
 	return SWITCH_STATUS_SUCCESS;
 }