various small updates

* new js_of_ocaml toplevel execution model
* minor changes to iocaml exception reporting (still a buffer fill up problem though)
* makefile stuff for 64-32 bit compilation + core_kernel tests

new notebooks require bigarray updates.
Add license.

iocamljs now only links against js_of_ocaml files so I think
a do anything with this project license is ok.

Things change fast with js_of_ocaml though....I should ask
permission.