Added support for direct input in WebIDL checker

Hi,

As you may know, I have set up an on-line tool to check the correctness
of WebIDL fragments embedded in HTML documents:
http://www.w3.org/2009/07/webidl-check (based on Aplix’s widlproc)

It is unfortunately not possible to use that tool on ReSpec.js-based
documents, since the tool works at the mark-up level rather than at the
DOM level, and adapting it to the mark-up used by ReSpec.js would imply
re-implementing the rather long and complex parsing algorithm
implemented by ReSpec.js in Python or XSLT.

As a workaround, I have added the possibility to copy and paste WebIDL
fragments in the tool; it’s not as convenient, but hopefully will it
still be somewhat useful.

Dom