jmod enhancements to support signed modules

[mark.reinhold at oracle.com]

> Date: Fri, 04 Jun 2010 14:47:01 +0100
> From: vincent.x.ryan at oracle.com

> http://cr.openjdk.java.net/~vinnie/6957907/webrev.01/

These changes look good.  Just a couple of comments on jmod-basic.sh:

  It'd be better to put the signed-module tests in a separate file, so
  that the "basic" tests remain basic.

  Can you create keystore.jks in the test script?  That'd be preferable
  to checking in a binary file.

Dalibor -- Could you please review this also?  There are some nontrivial
changes to the packaging code.

- Mark