GtkPopover: inherit actions from the relative_to widget

Make the relative_to widget the parent for a GtkPopover's
GtkActionGroup. This, for example, makes the menu model of a
GtkMenuButton find action groups attached to the button.

https://bugzilla.gnome.org/show_bug.cgi?id=729915
gtk-demo: Don't use margin-left/right

Instead, use margin-start/end, which are the non-deprecated
replacements.
gtk3-demo: Drop unneeded gtk_init() call

GtkApplication is doing this for us.
Minor documentation edit
gdk: Add new _gdk_set_window_state

Wayland's mechanism tells us all of our new states, rather than
telling us which ones were added and removed. Add a new private
interface so that we can simply specify the new states as a
bitfield directly rather than having to compute which ones were
added and removed.
wayland: Update to latest xdg-shell protocol
gtk3-demo: Fix up toolpalette demo

The demo appears pretty broken, because some icons are not fitting
well in the grid. Just skip the problematic icons.
GtkButton: Deprecate xalign and yalign properties

These are directly passed through to GtkMisc/GtkAlignment, which
are both on the way to deprecation.
Inspector: Fix make dist
GtkMenuItem: Stop using gtk_misc_set_alignment

GtkMisc is heading for deprecation. Just use GtkWidget h/valign.
https://bugzilla.gnome.org/show_bug.cgi?id=650762
GtkLabel: Drop references to GtkMisc

GtkMisc is heading for retirement. Point to the GtkWidget h/valign
properties instead.
Drop most uses of GtkMisc in tests

Replace them by GtkWidget h/valign. The only remaining uses
are those where a size group is involved; they can't be replaced
until GtkLabel stops looking at GtkMisc alignment for size
allocation.
Deprecate GtkMisc

This has been dangling ever since 3.0.
Avoid deprecation warnings

This is testing deprecated API, after all...
Add an alternative keybinding for the inspector

Control-Shift-I is already used for similar things in many
applications, so provide Control-Shift-D as an alternative.
https://bugzilla.gnome.org/show_bug.cgi?id=730043
Improve the GTK_STYLE_PROVIDER_PRIORITY_FALLBACK docs

Explain possible gotcha with catch-all rules.
Minor doc fixup
treestore: Fix segfault when reordering non-existing children

Calling gtk_tree_store_reorder() on a node without children would cause a
segfault; Fixes https://bugzilla.gnome.org/show_bug.cgi?id=698396

Signed-off-by: Olivier Brunel <jjk@jjacky.com>
Add a test for the previous fix
Fix a leftover deprecation warning