only, the the advanced prefs panel. This is not a pref, but UI that has the
following semantics:
when the panel loads, if there is a shortcut in the windows startup folder for
turbo mode, the checkbox in the UI is set. Otherwise, it is clear,
when the user hits OK, if the checkbox is not set, the shortcut is removed, if
necessary. Otherwise, if the checkbox is set, the shortcut is added, if necessary.
r=ssu, sr=mscott, a=asa
