Until liberator.NEW_BACKGROUND_TAB operates differently based on the
setting of browser.tabs.loadInBackground, this code must remain. At
the moment, NEW_BACKGROUND_TAB only opens a true background tab if
loadInBackground=true. When loadInBackground=false, the meaning of
NEW_TAB and NEW_BACKGROUND_TAB flip. Hence, until they're invariant,
something like ;F (which must always load tabs in the background)
has to pay attention to loadInBackground.