W32: correctly guess max window size from the size of the workarea of the screen it's on

Get monitor on which the most of the window is located (nearest monitor if
window is not on screen), get its work area (area not occupied by taskbar or
any other bars) and use that for maxsize.

Previous default of 30000 meant that windows maximized onto full screen,
even covering the area where taskbar is.

https://bugzilla.gnome.org/show_bug.cgi?id=726592
wayland: The xdg_surface.delete event was renamed to close
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