[Nestmates] Draft core reflection API

[David Holmes]

For comment:

http://cr.openjdk.java.net/~dholmes/8188075/webrev/raw_files/new/java/lang/Class.html#getNestHost()

Three functions added:
- getNestHost
- isNestmateOf
- getNestMembers

The first two never throw exceptions related to nest hosts or nest 
membership. The third does.

Thanks,
David