Fix saving persistent database on Windows.

Thanks to Daniel Degasperi.

ChangeLog.txt

@@ -4,6 +4,7 @@
 Broker:
 - Fix possible memory leak when using a topic that has a leading slash. Fixes
   bug #1360985.
+- Fix saving persistent database on Windows.
 
 Client library:
 - Fix mutex being incorrectly passed by value. Fixes bug #1373785.

src/persist.c

@@ -402,6 +402,12 @@ int mqtt3_db_backup(struct mosquitto_db *db, bool cleanup, bool shutdown)
 
 	fclose(db_fptr);
 
+#ifdef WIN32
+	if(remove(db->config->persistence_filepath) != 0){
+		goto error;
+	}
+}
+#endif
 	if(rename(outfile, db->config->persistence_filepath) != 0){
 		goto error;
 	}