Merge

6507179: javadoc -source 1.3 does not work with jdk6 Reviewed-by: mcimadamore

6294779: Problem with interface inheritance and covariant return types Summary: Problematic overriding check when two methods defined in two distinct superinterfaces are overriden by an interface Reviewed-by: jjg

6716866: some javac regression tests fail to compile with re-orged file manager Reviewed-by: darcy