tools: Check in tools for shrinking ICU size, change default to small-icu

* Change configure default to "small-icu" (Intl on, English only)
* add "--without-intl" and "vcbuild without-intl" options, equivalent
to --with-intl=none
* update BUILDING.md with above changes
* Checks in tools that generate the deps/icu-small source directory
from ICU source
* Tools and process for updating ICU documented in tools/icu/README.md

Fixes: https://github.com/nodejs/node/issues/3476
PR-URL: https://github.com/nodejs/node/pull/6088


Reviewed-By: James M Snell <jasnell@gmail.com>