8076543: Add @modules as needed to the langtools tests
Reviewed-by: jjg, shurailine

8029240: Default methods not always visible under -source 7
Reviewed-by: jjg

7192246: Add type-checking support for default methods
Summary: Add type-checking support for default methods as per Featherweight-Defender document
Reviewed-by: jjg, dlsmith

7046348: Regression: javac complains of missing classfile for a seemingly unrelated interface
Summary: Types.implementation forces unnecessary symbol completion on superinterfaces of a given type
Reviewed-by: jjg