can t/op/fork.t patch please make it into 5.18

Every time I've tried building perl 5.17.x, 'make test' has failed
because of t/op/fork.t (on RHEL)

Patch mentioned in
  http://www.nntp.perl.org/group/perl.perl5.porters/2013/05/msg201627.html
referring to
  https://rt.perl.org/rt3/Public/Bug/Display.html?id=117141



I'm not expecting this issue to be dealt with, but for a few years now,
lib/Benchmark.t would occasionally fail for VMWare hosts, so I now patch
it to change
   $delta from 0.4 -> 0.99

• can t/op/fork.t patch please make it into 5.18 by Danny Thomas