RFR: 8232650: ZGC: Add initialization hooks for OS specific code

[Per Liden]

Looks good.

/Per

On 10/21/19 4:37 PM, Stefan Karlsson wrote:
> Hi all,
> 
> Please review this patch to add initialization hooks for OS specific code.
> 
> https://cr.openjdk.java.net/~stefank/8232650/webrev.01/
> https://bugs.openjdk.java.net/browse/JDK-8232650
> 
> These hooks are needed to for a Windows port. ZInitialize allows 
> syscalls to be dynamically resolved. ZVirtualMemory allows callbacks 
> from 8232649 to be initialized.
> 
> Thanks,
> StefanK