JDK 15 RF(pre)R of JDK-8241374: add Math.absExact

[Chris Hegarty]

> On 30 Mar 2020, at 18:53, Joe Darcy <joe.darcy at oracle.com> wrote:
> 
> Hello,
> 
> Updated webrev at:
> 
>     http://cr.openjdk.java.net/~darcy/8241374.1/ <http://cr.openjdk.java.net/~darcy/8241374.1/>
LGTM.

-Chris.