Fix issue #13
Fix issue #13

Fixed by performing obfuscation of variables in NumericForStatement (which should have happened anyway). 

Verified by running this script (1,000,000 attempts) a few times:

```
for i = 1,1000000 do
	local st, ast = ParseLua('local table_ = { } for i = #table_,1,-1 do print(table_[i]) end')
	if not st then error(ast) end
	local m = Format_Mini(ast)
	--print("mini: ", m)
	if m then
		local a = m:gmatch("local i")()
		local b = m:gmatch("for i")()
		if a and b and a == b then
			print("They both contain 'i':", m)
			break
		end
	end
end
```
stravant/LuaMinify,tst2005/LuaMinify