Fix a bug found during review.

Fix a bug found during review.
Whilst the old version is what is defined in the spec, the definition in the spec does not agree with the description and associatedcomments in the spec. I have raised this as https://uel.dev.java.net/issues/show_bug.cgi?id=10
Modify the parser on the basis that the textual description and comments in the spec are correct and the production for StringLiteral is wrong

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@897629 13f79535-47bb-0310-9956-ffa450edef68