RFR (M) 8061651 - Interface to the Lookup Index Cache to improve URLClassPath search time

[Ioi Lam]

Please review this fix:

http://cr.openjdk.java.net/~iklam/8061651-lookup-index-open-v1/

Bug: Add an interface to the JVM's Class/Resource Lookup Index Cache for 
improving sun.misc.URLClassPath search time

     https://bugs.openjdk.java.net/browse/JDK-8061651

Summary of fix:

     Some J2EE environments have lots of JAR files in the
     classpath. However, during run-time, most classes are loaded by
     custom classloaders which delegate to the system loader. As a
     result, each class loaded by a custom classloader will cause many
     JAR search failures (in sun.misc.URLClassPath).

     To limit the number of searches in URLClassPath, the 8uX HotSpot
     VM is going to include a Class/Resource Lookup Index Cache that
     records information about the class/resource entries in the JAR
     files in the classpath. This can be used to improve
     sun.misc.URLClassPath search time.

     This is part 1 of the REF -- we are adding appropriate interfaces
     in both the JDK code and the HotSpot code to access this cache.

     URLClassPath.java is modified to use JNI to call into the HotSpot
     JVM_XXX APIs to access the cache.

     The implementation of this cache is done in part 2 of this RFE.

     Note that this enhancement is for JDK 8uX only. In JDK9 and
     beyond, we are considering an alternative implementation where the
     cache is maintained in the core libs code, outside of HotSpot.

Tests:

     JPRT
     Adhoc SQE tests

Thanks
- Ioi