More ports from aria-toolkit and enhancements

* Implicit semantics
* More audits:
 * RequiredOwnedAriaRoleMissing
 * DuplicateId
 * RoleNotScoped
 * BadAriaAttribute
 * UnsupportedAriaAttribute
 * AriaOnReservedElement
* Fixed BadAriaRole audit to handle abstract roles
* Several supporting changes and optimizations to utility methods and constants.
* A few minor formatting tweaks

nit: else on same line as }
http://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Conditionals