add: AST viewer tool, benchmarks of unittests change: some little style refactorings

### AST viewer
i'm currently tracking down a bug (most likely related to the rewrite operation of the AST) so i wrote this handy tool

### Benchmarks for unittests
I was curious how long certain codes need to compile/lex

### Style refactorings
We have *contains* - no need for the JS style *indexOf() != -1*