RFF (12): JDK-8207954: Data for --release 11

[Jan Lahoda]

Hi,

To support --release 11 in JDK 12, historical data for JDK 11 need to be 
added. As new attributes (NestHost and NestMembers) have been added to 
the classfile, there also needs to be some tweaking of the tool that 
creates the historical descriptions and the ct.sym sigfiles.

The proposed patch has two parts:
-code changes, which include:
--update to the build scripts and the tool, so that the tool can read 
both the open and extra/closed description of the ct.sym content, and 
merge those (there should not be any extra/closed for JDK 11, AFAIK, so 
this is to avoid having to update the closed part).
--improving the description on how to add historical data for new 
releases, using the new source launcher
--adding support for the new NestHost/NestMembers attributes
--adding a new test which strives to fail when a new attribute is added 
and CreateSymbols is not updated
http://cr.openjdk.java.net/~jlahoda/8207954/webrev.code.00/

-addition of the historical data:
http://cr.openjdk.java.net/~jlahoda/8207954/webrev.data.00/
(these may need to be re-generated when the final JDK 11 is released in 
case there are any changes, but that should be very simple)

JBS: https://bugs.openjdk.java.net/browse/JDK-8207954

Any feedback is welcome,
      Jan