增加SyntaxTree中的hash函数

git-svn-id: http://qlanguage.googlecode.com/svn/trunk@287 6d982bb3-a5a7-393d-ffc5-582415be9c85
README

git-svn-id: http://qlanguage.googlecode.com/svn/trunk@288 6d982bb3-a5a7-393d-ffc5-582415be9c85