webidl-check: Refactor request setup.

This eliminates some code duplication, and reuses some code from
htmldiff, so we already know it works.  I also switched from the
deprecated new module to the types module.
webidl-check: Refactor IDL error handling.

To remove duplicate code.
webidl-check: Remove CVS cruft.
Merge pull request #13 from brettcs/refactor-2014-02

Minor refactoring