check the new StackMapTable feature for usage in Groovy

java 6 has a new verifier, that operates in two faces. the first phase is done by the compiler, which has to store type information in stack maps. the second phase is when loading the class, the verifier will check the usage based on the type information from the first phase. This allows the verifier to run much faster and shortens class loading time.

This feature should be checked for usage in Groovy.