Add autotools support

Some differences from previous diff:

* Added LICENSE and COPYING.  I merely copied over the existing native_client LICENSE, as required, but we need to specify how we are licensing our changes.
* Moved some of the top-level cruft to the "config" directory, so a lot of the autogenerated tools will no longer be in the root of the project.
* Added a pkg-config .pc for libvalidator.
* Defaulted builds to quiet.  Can be verbose with "make V=1"

Redhat and debian packaging probably need to add the .pc file, and we still need a header for the public validator functions.