Review Request for 6878481: Add performance counters in the JDK

[Mandy Chung]

This is related to 6857194: Add hotspot new perf counters to aid class 
loading performance measurement.

It's useful to add performance counters in the library code so that perf 
data from the JDK and VM can be collected and output in a unified way 
(written in the jvmstat shared memory buffer).  I add a simple 
sun.misc.PerfCounter class to maintain the list of perf counters for the 
library to use.  This fix only instruments the class loading and jar/zip 
to collect simple basic metrics.   Additional perf counters will be 
added in the future.

Webrev:
     http://cr.openjdk.java.net/~mchung/6878481/webrev.00/

Thanks
Mandy