Review Request (S) 8014288: perf regression in nashorn JDK-8008448.js test after 8008511 changes

[serguei.spitsyn at oracle.com]

Please, review the fix for:
   bug: http://bugs.sun.com/view_bug.do?bug_id=8014288
   jbs: https://jbs.oracle.com/bugs/browse/JDK-8014288

Open webrev:
http://cr.openjdk.java.net/~sspitsyn/webrevs/2013/hotspot/8014288-JVMTI-JSR292.1/

Summary:
   The fix of the 8008511 introduced a performance regression for the 
Nashorn tests.
   The fix is to use method_idnum() for direct indexing into the 
MemberNameTable
   that replaces a linear search caused the regression.
   No new regression test is needed as the Nashorn tests show the 
performance is back to normal.

Testing:
   The vm/mlvm and Nashorn tests

Thanks,
Serguei