Small unclarity in JVMS re absence of ACC_INTERFACE

[Alex Buckley]

Thanks for the comment. In JVMS 4.1, I have strengthened the 
presentation of how class files are partitioned into ACC_MODULE-set 
versus ACC_MODULE-not-set. This addresses the specific comment as well 
as other comments that could have been raised about the disjointness of 
classes, interfaces, and modules.

Alex