GROOVY-6350: fixes NPE and removes the debug code from before

Conflicts:

	src/main/org/codehaus/groovy/transform/stc/StaticTypeCheckingVisitor.java
GROOVY-6282: try fixing super constructor selection in case of the super class being on the classpath
fixing joint build groovy-grails build and adapting error message to changed ClassNode#toString
some more stub generator tweaks