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
Are RTTI and exception support necessary?  If that's the case, can exceptions escape from ICU?  That would be problematic because everything else is compiled without unwind support.