This feature is a stage 3 proposal implemented as a
wrapper around ICU that categorizes singular/plural/etc
grammatical forms based on a number and locale.

Based on littledan's work started here:
https://codereview.chromium.org/2736543002/

Bug: v8:5601
Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: I4107cd28be72413ec43aa1ff0f4fe6e181a290f4
Reviewed-on: https://chromium-review.googlesource.com/562298
Commit-Queue: Josh Wolfe <jwolfe@igalia.com>
Reviewed-by: Daniel Ehrenberg <littledan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47485}