RFR: 8171373: Reduce copying during initialization of ModuleHashes

[Chris Hegarty]

> On 16 Dec 2016, at 16:00, Claes Redestad <claes.redestad at oracle.com> wrote:
> 
> Hi,
> 
> recent changes to split out ModuleHashes from ModuleDescriptor caused a small/tiny increase in HashMap creation, resize and copying:
> 
> Webrev: http://cr.openjdk.java.net/~redestad/8171373/webrev.01/
> Bug: https://bugs.openjdk.java.net/browse/JDK-8171373
> 
> This decreases #bytecode executed during startup by ~20K (around 1.5% of total).

Nicely done Claes. Looks good to me.

Builder.nameToHash can be final, no?

-Chris.