RFR(13): JDK-8216263: Add historical data for JDK 12

[Jan Lahoda]

Hi,

To make --release 12 work, we need to add historical data for JDK 12. 
The current historical data is based on:
$ javac  -fullversion
javac full version "12-ea+26"

We may need to update the data once JDK 12 is out to cover any changes 
to the APIs that might happen.

The patch also adds a simple (shell) script to generate the data, so all 
that was needed to generate the data was:
$ cd make/data/symbols
$ sh generate-data <path-to-JDK-12>

JBS: https://bugs.openjdk.java.net/browse/JDK-8216263
Webrev: http://cr.openjdk.java.net/~jlahoda/8216263/webrev.00/

How does this look?

Thanks,
     Jan