Bogus global variable access in XSSFilter:init

[agladysh]

args = args or {}

https://github.com/yuri/lua-xssfilter/blob/master/lua/xssfilter.lua#L144

Please remove, as it messes with our global environment protection.

Would be also cool to get rid of module() (in favor of return {}) and to alias all globals at the top of the file for better sandboxing support.