RFR: 8189389: Move heap creation into GC interface

[Roman Kennke]

> This moves the heap creation code that is currently inside 
> universe.cpp to the GC specific GCArguments subclasses, thus reducing 
> GC specific stuff in shared code. It's based on top of 8189171 which 
> should arrive in the repo today or very soon.
>
> http://cr.openjdk.java.net/~rkennke/8189389/webrev.00/ 
> <http://cr.openjdk.java.net/%7Erkennke/8189389/webrev.00/>
>
> Test: hotspot_gc
>
> Ok?
>
> Roman
>
Ping?