RFR: 8231552: ZGC: Refine address space reservation

[Per Liden]

Updated webrev after off-line comments from Stefan and Erik.

Full: http://cr.openjdk.java.net/~pliden/8231552/webrev.3
Diff: http://cr.openjdk.java.net/~pliden/8231552/webrev.3-diff

/Per

On 10/16/19 10:41 AM, Per Liden wrote:
> Latest version of this patch, rebased on today's jdk/jdk:
> 
> http://cr.openjdk.java.net/~pliden/8231552/webrev.2
> 
> /Per
> 
> On 10/3/19 11:45 AM, Per Liden wrote:
>> We could be slightly more sophisticated and do a better job reserving 
>> address space in situations where parts of the address space is 
>> already occupied or when the process is running with address space 
>> limitations.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8231552
>> Webrev: http://cr.openjdk.java.net/~pliden/8231552/webrev.0
>>
>> /Per