JDK 9's source code is now modular

[mark.reinhold at oracle.com]

FYI, the changesets for JEP 201: Modular Source Code were merged earlier
today, so if you're working on JDK 9 then your forest will have a very
different structure after your next pull.  See the JEP for details
(http://openjdk.java.net/jeps/201); a related subtask has links to the
Mercurial changesets (https://bugs.openjdk.java.net/browse/JDK-8054834).

My thanks to Alan Bateman and Mandy Chung for their work over the last
several years to tease out the modular structure that's been hiding all
along inside the massive, monolithic JDK; to Erik Joelsson for rewriting
the build system (again!) to accommodate modules; and to Chris Hegarty
for wrangling patches and attending to the myriad details of landing
this huge change in JDK 9.

- Mark