Code Review Request for two pass signing

[Sean Mullan]

I have modified the signed module implementation to generate a signed module 
file in two passes, which avoids the signature length issues mentioned in a 
previous thread [1].

I also enhanced some of the code to use the new JDK 7 try-with-resource and 
multi-catch language features.

webrev: http://cr.openjdk.java.net/~mullan/jigsaw/webrevs/twopass-sign/webrev.00/

Thanks,
Sean

[1] http://mail.openjdk.java.net/pipermail/jigsaw-dev/2011-April/001240.html