UI freeze break request for gnome-shell

[Giovanni Campagna <scampa giovanni gmail com>]

Hello release team,

As promised, I'm here again with another request for UI freeze break.
This time, it's about https://bugzilla.gnome.org/show_bug.cgi?id=682544
What it does is replacing the "Authentication failed" banner
notification on password failure, as well as other PAM messages, in
gdm and in the unlock dialog with an orange prompt below the entry, in
the style of the mockup at
https://github.com/gnome-design-team/gnome-mockups/raw/master/system-lock-login-boot/authentication-failure.png
, except without the icon.
The feature is listed in the BoF page at priority 0 for the login dialog.
I had this prepared for 3.5.91, but a required gdm change appeared
after gnome-shell 3.5.91 was released, so this won't make it, unless a
3.5.91.1 is released.

Thanks in advance

Giovanni