MAINT-1444: Make bottom-right corner of new login panel overlap.

MAINT-1444 complains that with all optional login-panel controls enabled, the
login panel is wider than 1024 pixels: at that width, the new "Start now"
button is pushed completely off the right edge of the window. Richard told me
how to tweak the layout so that the controls can squeeze together in an
overlapping way, enabling all controls to be visible even at 1024 width.