Adwaita: take named colors out of _colors.scss

To be able to use sass for shipped css, importing _colors.scss
and _drawings.scss.
css: Implement font-stretch

The font-stretch CSS property is defined in the Level 3 CSS Fonts
module, available at:

  http://dev.w3.org/csswg/css-fonts/#propdef-font-stretch

It allows defining a normal, condensed, or expanded face to the font
description. Pango already supports it, so this is literally just the
CSS parser machinery needed to bridge our CSS to the FontDescription
API.

https://bugzilla.gnome.org/show_bug.cgi?id=735593
Adwaita: border rationalization and cleanup

Rely only on border-style for border, take out border-width and
border-style from drawing functions.
tooltip: Use subsurfaces on wayland

This places tooltips in the right place, and avoids having those attempt
to steal the focus.

https://bugzilla.gnome.org/show_bug.cgi?id=735531
scrolledwindow: Be smarter at invalidating overshoot areas

The previous way to invalidate was meant to work on the overshoot window
so it wouldn't be as taxing. Since the overshoot window is gone, this
would invalidate way more than intended. So constrain invalidated areas
to the sides where overshoot is happenning at that moment.

https://bugzilla.gnome.org/show_bug.cgi?id=735223
Updated Hebrew properties translation
Adwaita: nicer transition for flat buttons.
quartz: Get default font size from user font

https://bugzilla.gnome.org/show_bug.cgi?id=735321
Adwaita: dim menu checks/radios a bit
menubutton: dismiss menu/popover when toggling programmatically

https://bugzilla.gnome.org/show_bug.cgi?id=735545
Adwaita: bring the separator back for dialog buttons

- separators got nuked during lapo's border cleanup
GtkDialog: Keep special-casing help buttons

We used to move help buttons to the secondary position regardless
how they were added to the action area. Keep doing that, to avoid
breaking existing dialogs that rely on this behavior.

https://bugzilla.gnome.org/show_bug.cgi?id=735119
GtkHeaderBar: Update separator visibility when needed

We need to be a little more forthcoming with showing and hiding
the separators - their visibility now depends on the the visibility
and pack type of the regular headerbar children. This was observed
in gnome-contacts, where headerbar buttons are shown and hidden.
Add a release note about X without render

This reflects the findings in
https://bugzilla.gnome.org/show_bug.cgi?id=735294
Adwaita: pathbar whitespace

- optically center icons + labels vertically. It isn't actually
  centered, but feels more balanced
- add some left/right padding

https://bugzilla.gnome.org/show_bug.cgi?id=734753
GtkAboutDialog: Support https in links

https://bugzilla.gnome.org/show_bug.cgi?id=680067
Adwaita: avoid text in buttons being overridden by GtkLabel style
Adwaita: style GtkLabel.separator

Fixes gnome-document search popup titles.
Adwaita: titlebutton are flat image-buttons

Hence treat them like those, a bunch of special case styling
removed, which also doesn't override selection mode buttons
styling.
Bump wayland dep to 1.5.91

This release has the new key repeat listener that we are using.