Adds a can_get_var wrapper

[Absolucy]

This simply adds an can_get_var wrapper - in SS13, it would be this:

/proc/wrap_lua_can_get_var(datum/thingymajig, var_name)
	SHOULD_NOT_SLEEP(TRUE)
	return thingymajig.can_vv_get(var_name)

This allows for improved safety with certain things, such as preventing Lua scripts from being used to leak, like, the DB connection info or something

[Absolucy]

... oh nvm this isn't worth the time