RFR: JDK-8202951: Implementation of JEPJDK-8204247: Include default CDS (Class Data Sharing) archive in JDK binary

[Jiangli Zhou]

Please review the implementation for JEP JDK-8204247 
(https://bugs.openjdk.java.net/browse/JDK-8204247). The goal of the JEP 
is to include a default CDS archive in JDK 12 binary distribution 
(downloadable from http://jdk.java.net/12/). The default CDS archive is 
generated using the default classlist (resides in the lib/ directory) at 
JDK build time. Any comments/suggestions are highly appreciated.

All makefile changes in the webrev are contributed by Erik Joelsson 
(many thanks!!).

This is a combination of efforts from different teams and individuals. 
Thanks to everyone who has been involved in the JEP & implementation 
discussions, testing and bug fixing!

   JEP: https://bugs.openjdk.java.net/browse/JDK-8204247
   RFE: https://bugs.openjdk.java.net/browse/JDK-8202951
   webrev: http://cr.openjdk.java.net/~jiangli/8202951/webrev.00/

Two sanity test cases for the default CDS archive are included 
test/hotspot/jtreg/runtime/SharedArchiveFile. They are not intended for 
in-depth CDS functional testing, which is already covered by the 
existing cds/appcds tests and all tiered tests executing with the 
default CDS archive enabled.

As part of the webrev, 
test/jdk/javax/imageio/plugins/png/ItxtUtf8Test.java is also fixed to 
use larger java heap (JDK-8209739
, https://bugs.openjdk.java.net/browse/JDK-8209739).

Tests executed:
  - several rounds of tier1 - tier8 via mach5
  - JCK lang, api and vm tests via mach5


Thanks!
Calvin, Ioi, Jiangli