background: Fix deprecated API usage

https://bugzilla.gnome.org/show_bug.cgi?id=740986
power: Fix deprecated API usage

https://bugzilla.gnome.org/show_bug.cgi?id=740986
color: Fix deprecated API usage

https://bugzilla.gnome.org/show_bug.cgi?id=740986
display: Drop deprecated API usage on FooScrollArea painting

This achieves a very similar result (darkening the background color)
without having to peek into the style context. Note that the stroke
is removed because it isn't really visible anyway.

https://bugzilla.gnome.org/show_bug.cgi?id=740986
display: Fix deprecated API usage

https://bugzilla.gnome.org/show_bug.cgi?id=740986
online-accounts: Fix deprecated API usage

https://bugzilla.gnome.org/show_bug.cgi?id=740986
region: Fix deprecated API usage

https://bugzilla.gnome.org/show_bug.cgi?id=740986
sound/speaker-test: Port to GtkGrid

https://bugzilla.gnome.org/show_bug.cgi?id=740986
user-accounts/photo-dialog: Remove needless frame

Now that the crop area isn't all black around the picture, this frame
is just visual noise.

https://bugzilla.gnome.org/show_bug.cgi?id=740986
user-account: Don't stroke the down arrow with the border color

Besides using deprecated gtk+ API this color is actually fully
transparent in the current GNOME theme, meaning that the arrow ended
up looking smaller than intended.

https://bugzilla.gnome.org/show_bug.cgi?id=740986
search: Drop deprecated API usage

https://bugzilla.gnome.org/show_bug.cgi?id=740986
privacy: Drop deprecated API usage

https://bugzilla.gnome.org/show_bug.cgi?id=740986
sharing: Drop deprecated API usage

https://bugzilla.gnome.org/show_bug.cgi?id=740986
wacom: Drop deprecated API usage

https://bugzilla.gnome.org/show_bug.cgi?id=740986
network: Drop deprecated API usage

https://bugzilla.gnome.org/show_bug.cgi?id=740986
configure: Bump gtk+ version requirement

Needed for gtk_label_get/set_xalign() .