RFR: JDK-8073152: Update Standard/ExtendedCharsets to work with module system

[Xueming Shen]

Hi,

Please help review the changes for  JDK-8073152

Issue: https://bugs.openjdk.java.net/browse/JDK-8073152
Webrev: http://cr.openjdk.java.net/~sherman/8073152/webrev/

This change is to re-organize how the "standard" and "extended" charsets 
repository are
built for the jdk/jre images. Before module system, the "standard" 
charset provider is built
into rt.jar and the "extended" charsets provider is in charsets.jar, 
which is located in the
"lib/ext" directory. both are available during the system boot time. In 
jigsaw, the extended
charsets provider is in jdk.charset (vs the "standard" is in java.base) 
module and might not
be "visible" during the early phase of system classes loading, which 
might cause problem
as some of the charsets now in "extended" charsets may needed during the 
boot stage. The
proposed change here is to re-organize the way these two providers are 
built, and put in the
mechanism that enable the build system to configure which group of 
charsets need to be
moved from the "extended" charsets into the "standard" (java.base), 
based on the target
platform, during the jdk build time.

The updates are

(1) to consolidate the existing configuration files "sbcs", "dbcs", 
"extsbcs" and
      "standard-charsets" (and the aliases table originally hardcoded in 
ExtendeardCharsets.java)
       into a single configuration file "charsets" to define all 
supported charsets, with their
       name, clz name,  history name, package name and all aliases
http://cr.openjdk.java.net/~sherman/8073152/webrev/make/data/charsetmapping/charsets.html

(2) in addition to the the "standard charsets" provider, now the 
"extended charsets" provider
      class is also built during the build time based on the new 
configuration file "charsets"

(3) to add a build-time mechanism to specify individual sun.nio.cs.ext 
charset to be built into
      "standard" charsets provider (sun.nio.cs package in java.base 
module), with os-specific
       configuration file, such as stdcs-linux, stdcs-windows and 
stdcs-solaris.

(4) to move DoubleByte, HKSCS and DelegatableDecoder classes into 
sun.nio.cs, so they can be
      used/referenced by those dbcs classes that might be moved into 
sun.nio.cs

(5) to change some sun.nio.cs.ext implementation java files to be a 
".template", so the real .java
      can be generated during build-time with correct pkg name and 
aliases info.

There are two leftover, gb18030 and euc_tw, these are two charsets with 
huge mapping table. Might
need special update to better fit into sun.nio.cs later.

thanks!
-Sherman