Review request JDK-8058367: Add verify-modules target to the default and images target

[Mandy Chung]

With the Modular Source Code [1] in JDK 9, the verify-modules target
was added in the build to catch any regression to the module boundaries.
It's important to catch this regression early during jdk development.
This patch proposes to add verify-modules to the default target
and also images target (it was a bug).  This will track the time
to determine if the build time becomes an issue.

Webrev at:
   http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8058367/webrev.00/

Mandy
[1] https://bugs.openjdk.java.net/browse/JDK-8051619