Review request for JDK-8134609: Allow constructors with same prototoype map to share the allocator map

[Marcus Lagergren]

Really great work, Hannes. +1 with Attila’s comments integrated.

/M

> On 16 Sep 2015, at 10:48, Hannes Wallnoefer <hannes.wallnoefer at oracle.com> wrote:
> 
> u suggested below I did some refactoring on the PropertyMap class, making more fields final to better reflect its immutable nature. I soon noticed that all the core fields (flags, field/spill boundaries, class name) could quite easily be made final except for the ne