RFR(S): 8232081: Try to link all classes during dynamic CDS dump

[Calvin Cheung]

JBS: https://bugs.openjdk.java.net/browse/JDK-8232081
webrev: http://cr.openjdk.java.net/~ccheung/jdk15/8232081/webrev.00/

The proposed changeset for this RFE adds a JVM_LinkClassesForCDS() 
function to be called from java/lang/Shutdown to notify the JVM to link 
the classes loaded by the builtin class loaders. The 
MetaspaceShared::link_and_cleanup_shared_classes() has been modified to 
handle both static and dynamic CDS dump. For dynamic CDS dump, only 
classes loaded by the builtin class loaders will be linked. Local 
performance testing using javac on HelloWorld.java shows an improvement 
of >5%.

Passed tier1 - 4 tests.

thanks,

Calvin