This implements support for named captures in
RegExp.prototype[@@replace] for when the replaceValue is callable.

In that case, the result.groups object is passed to the replacer
function as the last argument.

BUG=v8:5437

Review-Url: https://codereview.chromium.org/2764343004
Cr-Commit-Position: refs/heads/master@{#44142}