reftests: I can't count in CSS

nth-child() is 1-indexed, not 0-indexed.

It doesn't matter for this test really, but better do it right to not confuse
poor developers who wonder why the first image is highlighted when nth-child(0)
clearly states "none".
textview: only set invalidate handler for text window.
pixelcache: add getter for extra width and height.
Updated Galician translations
Tajik translation updated
Tajik translation updated
Tajik translation updated
Updated Norwegian bokmål translation
Add a testcase for custom levels in GtkLevelBar

This is related to https://bugzilla.gnome.org/show_bug.cgi?id=707695
Add a test for icons in menu models

testmenubutton now features an icon.
textview: use pixelcache rendered area to inform invalidation region.

Use the pixelcache rendered area to inform what part of the cache should
be invalidated upon changes to the underlying textlayout.

By rendering the background to the pixelcache, we can avoid the need to
use RGBA content.

Also, we're using the pixel cache on the text windows bin_window (see
gtk_text_view_get_window) so we need to register the invalidation handler
on that, otherwise the region passed to the invalidate handler will get
clipped to the visible region.

https://bugzilla.gnome.org/show_bug.cgi?id=707244
Pixel cache: Add no-pixel-cache debug flag

This is useful for benchmarking comparisons, and to verify if bugs
happend with or without the pixel cache.
pango: Handle case where pango_layout_get_text() returns NULL

Fixes crashers with accessibility

https://bugzilla.gnome.org/show_bug.cgi?id=707659
Revert "pango: Handle case where pango_layout_get_text() returns NULL"

This reverts commit 70ac2b24c3d400c854d8a9e0937afa076f9dbe7f.

It turns out the correct fix is to make pango_layout_get_text() not
return NULL. This has been done, so we can drop this patch.

I won't bump the Pango dependency in configure.ac for this as I don't
consider the crash critical enough.