Detect unused variables

[Namespace]

No interest, I see.
I improved the code again. Now, even user-defined types, and 
(associative) arrays detected.
I'm sure there are a lot of situations where my code will fail, 
but I will continue working on it.
Therefore criticisms and suggestions were really helpful.

The new code: http://codepad.org/lvAFx4oP

And two new test files:
http://codepad.org/SgezNiYm
http://codepad.org/y2NYrEgt