Rebase+test Firefox patches to 10.0.x-ESR for TBB stable
I've been convinced that we should be tracking 10.0 ESR for TBB stable by some anonymous cypherpunk in #5737 (closed). I should test rebasing the current set of Firefox patches to 10.0.x ESR and see how it works out. If it seems to work, I think we should switch over for TBB 2.2.x (but keep tracking Rapid Release for TBB 2.3.x-alpha).