RFR (XS) 8184762: ZapStackSegments should use optimized memset

[Aleksey Shipilev]

On 07/17/2017 09:18 PM, Roman Kennke wrote:
> I'd probably declare the constant char or jubyte or such
> (fill_to_bytes() takes a jubyte, can't say I like the j*types much).
> (breaks 'consistency' with other similar constants though... your call)

Yes, I kept it as "int" for consistency.

> Update copyright header.

Updated:
  http://cr.openjdk.java.net/~shade/8184762/webrev.02/

Thanks,
-Aleksey