Fixed e4x removal.

Now using document.createDocumentFragment instead of
document.implementation.createDocument, so we don't get
HierarchyErrors any more. The probable error was that the document
created with createDocument was not compatible with the node that it
was inserted into (i.e. you can't insert a whole document into another
document).
Misc bug fixes

Added trace to warnUserAboutBeingUnderAttack, fixed text display in WarnUserDlg.xul
Updated plugin certificate.
Added emacs js-indent-level lines

Nicer for me (Jan), and I hope it doesn't iannoy anyone.