Make `options` local here.

Undoubtably this may cause problems later if unchecked.

```
2016-03-22 21:57:52: WARNING[Server]: Assignment to undeclared global "options" inside a function at .../sofar/git/minetest/bin/../builtin/game/chatcommands.lua:862.
```

builtin/game/chatcommands.lua

@@ -859,7 +859,7 @@ core.register_chatcommand("clearobjects", {
 	description = "clear all objects in world",
 	privs = {server=true},
 	func = function(name, param)
-		options = {}
+		local options = {}
 		if param == "" or param == "full" then
 			options.mode = "full"
 		elseif param == "quick" then