Grails 2.4 + Groovy 2.3 + J8 Grails project compiler errors

Andy, Kris
This would fix the compiler errors for new Grails project. JDTMethodNode(s) are made abstract if they belong to an interface. I excluded default and static methods from this check.
Default is added for J8 support only, hence to be sure not to break the build i put as 0x10000 and make a comment on what that magic value is. The change is for Groovy JDT patch for e43j8.