It doesn't appear these IDL files have had interfaces in them since
before the Netscape import, and were mostly just hanging around
because they contained some IDs needed elsewhere. Move the IDs
somewhere more appropriate and remove files.
MozReview-Commit-ID: AINtTerqHu1
Differential Revision: https://phabricator.services.mozilla.com/D2688
--HG--
extra : moz-landing-system : lando
