RFR (S) 8194246: JVM crashes when calling getStackTrace if stack contains a method that is a member of a very large class

[coleen.phillimore at oracle.com]

Summary: Use unsigned short to save method_id in stack trace.

Tested with tier1 tests and test provided.  jck testing in progress.

open webrev at http://cr.openjdk.java.net/~coleenp/8194246.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8194246

thanks,
Coleen