RFR (sh/jdk): Fix evac-lock shift

[Aleksey Shipilev]

On 6/29/20 2:05 PM, Roman Kennke wrote:
> I made a mistake in computing the evac-lock-shift. I wrongly assumed
> that pointer_delta(a, b) gives me the byte-difference between b and a,
> but it really gives the pointer different in units of the type of a and
> b. (Why is it not ok to use C++ pointer math there?!) This makes
> calculation of the _shifter wrong. Fix:
> 
> http://cr.openjdk.java.net/~rkennke/fix-evac-lock-shift/webrev.00/

Did the same thing a few hours ago:
 https://mail.openjdk.java.net/pipermail/shenandoah-dev/2020-June/012573.html

...but also put the new default so it matches the current behavior (which seems already good), and
updated the flags.

-- 
Thanks,
-Aleksey