A couple more freeze break requests for gnome-shell

[Florian Müllner <fmuellner gnome org>]

Hi again,

here are some more freeze break requests - I wouldn't consider any of
them critical, but they are nice-to-have and trivial:

  https://bugzilla.gnome.org/show_bug.cgi?id=684727
  https://bugzilla.gnome.org/show_bug.cgi?id=684728
     Two one-line fixes for accessibility issues on the login-screen -
the first one also introduces a new string ("Power") for
     the accessible name of the right-most item in the top bar

  https://bugzilla.gnome.org/show_bug.cgi?id=684611
     Fixes a problem where we incorrectly show the input volume in the
lock-screen


Thanks,
Florian