* Add a `fastmap` crate that provides the H256FastMap specialized HashMap
* Use `fastmap` instead of `plain_hasher`
* Update submodules for Reasons™
* Submodule update
* Update `add_license` script
* run script
* add `remove duplicate lines script` and run it
* Revert changes `English spaces`
* strip whitespaces
* Revert `GPL` in files with `apache/mit license`
* don't append `gpl license` in files with other lic
* Don't append `gpl header` in files with other lic.
* re-ran script
* include c and cpp files too
* remove duplicate header
* rebase nit
