Clarified copyright situation and fixed source headers

Fixes #115, thanks @josch
syntax: add support for `bitstring'

Add support for the `bitmatch' syntax extension of the ocaml-bitstring (https://code.google.com/p/bitstring/) library.
Merge pull request #126 from nojb/master

syntax: add support for `bitstring'
Added tests for minor bugs in some Async indentation and nested try-with blocks.