dropped symbols in libxul.so in Firefox 27

Hi,

I'm the maintainer of the GWT Developer plugin for Firefox, which is quite
creaky and uses internal Firefox API's. I noticed that a bunch of
JavaScript-related symbols were dropped in Firefox 27 [1]. They're still
there in XulRunner's version of libxul.so.

I'd just like to confirm that this is intentional and get the technical
details behind the change. (We've known for a while that we can't maintain
this plugin forever, but I'd like something tell to my users.)

- Brian

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=965998