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"
  - [x] Enable use of any ICU (not just special SRL branch) - will probably do this by
      - [x] copying iculslocs.c and icutrim.py into node
      - [x] making the unixy build work the same way as windows.
      - [x] update the instructions to say "grab an ICU tarball, unpack as `deps/icu`, enjoy"
- 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
    - [x] the "smaller ICU" changes could be pushed into a future ICU version. (already have bugs filed for this, not a blocker here)

NB: I have signed the CLA, you will find me under `srloomis` at US dot IBM dot COM
So, it seems this has no actual upstream repository, but we're considering this an external dependency because the intent is to have this merged up into another upstream repository? If this code only exists just for Node then possibly it should go in `src/icu/` or some such instead?