build: i18n: rename English to 'certain' only

this prepares for srl295/node#10 choosing the locale.
build: i18n: add   --with-icu-locales option

this lets you choose which locales are used in the `small-icu` case

Example:

  configure --with-intl=small-icu  --with-icu-locales=tlh,grc,nl

Note that the unit test tests/simple/test-intl.js hasn't been updated
yet.

This mostly fixes srl295/node#10

(Also note that as of this writing, neither Klingon nor Ancient Greek
are in upstream CLDR data. Serving suggestion only.)