example: Don't set a nonexisting property

The GtkHeaderBar::show-fallback-app-menu property does not exist,
and isn't needed anyway.
example: Fix up margins

This makes the code match what we show in the screenshots. This
broke when headerbars were changed to allow titles to extend into
the margin.
example: Fix indentation
example: Port to gtk_application_set_accels_for_action

Instead of hardcoding an accelerator in the ui file, use
gtk_application_set_accels_for_action.
example: Modernize the prefs dialog

We should show the current best practice for this kind of
dialog, and use a headerbar with a window close button.
example: Make search button square

The image-button style class takes care of it.
example: Make gears button square

Another application of image-button.
example: Use popover for gears menu
example: Update screenshots
broadway backend: allow building on OpenBSD

On OpenBSD shm_open(3) is part of libc and there is not librt, so add an
according check.
Check if we have posix_fallocate before using it.

https://bugzilla.gnome.org/show_bug.cgi?id=728272
Added bindings support to GtkBuilder by introducing 3 new <property> attributes "bind-source" to specify the source object of the binding "bind-property" to specify the source property and "bind-flags" to specify the binding flags (optional)

Binding an object sensitive property with a check button active property will look like this:

<object class="GtkButton" id="button">
  <property name="sensitive" bind-source="checkbutton" bind-property="active"/>
</object>

This is based on the original work done by Denis Washington for his GSoC project

This closes Bug 654417 "[GSoC] Add <binding> element to GtkBuilder syntax"
Updated German translation
Fixed Russian translation
docs: Fix parameter names for two functions

Don't use two different parameter names.
Add a style class to model buttons

This will let us stop using the class name in Adwaita, and will
help with some future additions.
Fix the build
GtkScaleButton: Don't specify a icon size of zero

This only works for scalable icons, but breaks if we fall
back to pngs.
gtk-demo: Make sure to clear the timeout when we stop it
wayland: Remove VISIBILITY_NOTIFY event

VISIBILITY_NOTIFY is already known to be unreliable.
wayland: Remove useless hint set