JLS spec changes for nestmates

[Dan Smith]

FYI, here are the spec changes for JLS related to nestmates.

http://cr.openjdk.java.net/~dlsmith/nestmates-jls.html

I've also attached them to the JBS subtask:
https://bugs.openjdk.java.net/browse/JDK-8177019

This is just some cleanup to more closely align the JLS description of method invocation with the actual (updated) JVMS rules.

I looked over 13.1, and think it does a fine job of allowing binaries to use the NestHost and NestMembers attributes without any changes (see items 9 and 10 in the second list).

—Dan