CFG ambiguity experiment

Repeatable experiment for the paper "Detecting Ambiguity in Programming Language Grammars" to appear at SLE 2013. Link to the paper: http://tratt.net/laurie/research/pubs/papers/vasudevan_tratt__detecting_ambiguity_in_programming_language_grammars.pdf《编程语言语法中歧义检测》一文的可重复实验，该文即将发表于2013年的SLE会议。