Move AstBuilderTransformation Global xForm to separate module

Hi,

Based on the dev mailing list thread: http://markmail.org/message/aiwgmjywhqr5edud, this is a request to move AstBuilderTransformation into a separate module, so that the general compilation of the groovy scripts, which don't have anything to do with AstBuilder, don't have to incur the cost of its processing.

I didn't really try to look for a general modularization effort JIRA. If there is one, may be this issue can become a sub-task there.

Thanks.