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