build: enable a smaller Intl (i18n / ICU) build

Implements joyent/node#7676 - see `README.md` for details.

Passes `make test` *as well as* current HEAD did (some network test failures?)

known TODOs:
- doc
  - [ ] Too much detail in the `README.md`. Move elsewhere/delete. 
- build
  - [x] Windows build? Rewrite `icu-generic.sh` in python and/or use cygwin?
      - [x] but, need to allow build of linked-in ICU data (large and small) in windows.
  - [x] Switch to turn on and off "little by default"
  - [ ] Enable use of any ICU (not just special SRL branch)
- v8 ( discussion here: https://groups.google.com/forum/#!topic/v8-dev/uAdEzPBcdXE ) 
  - [x] need `InitializeICU` function https://code.google.com/p/v8/issues/detail?id=3344  ( workaround: could call the ICU functions directly from node..    )  *Update: v8's preference may be that node call into ICU directly here for setup. Fine, I can move that code out of deps/v8 and into node.cc or elsewhere. *
  - [x] bug fixes to v8  https://code.google.com/p/v8/issues/detail?id=3348  *not a hard dependency, I can take this out of the PR*
  - [x] Save 1M by turning off breakiterator if unneeded https://code.google.com/p/v8/issues/detail?id=3345   *This saves 1M - but can pull it out of the PR also. *
- ICU
    - [ ] the "smaller ICU" changes could be pushed into a future ICU version.

NB: I have signed the CLA, you will find me under `srloomis` at US dot IBM dot COM
(thanks for the comments) about 500k of data (not counting the Chinese character mapping which is not normally built) but until it is exposed in v8, either ES402 or a v8_ specific thing (as break iteration is), it won't do node any good.

Speaking of v8 and this line, when https://code.google.com/p/v8/issues/detail?id=3345 is fixed (need to follow up with a specific patch) then break iteration can be turned off if not needed (it's not in the standard Intl interface, but may be added later)