GtkApplication: load gtk/menus-common.ui resource

Allow the app to install a resource called gtk/menus-common.ui which
will always be loaded, regardless of which type of menus we are using.

https://bugzilla.gnome.org/show_bug.cgi?id=733925
doap category core
GtkPopover: Properly update a11y parent

When the relative-to widget changes, update the accessible parent
of the popovers accessible.

https://bugzilla.gnome.org/show_bug.cgi?id=733923
Add a test for popover accessible parents

This tests the fix in the previous commit.
inspector: Make the action editor more useful

We were not finding the action owner for menuitems, we have to
try harder to walk all the way up to the window.
GtkImage: Always close the loader

This was causing some tests to fail with a critical.
css: Don't infloop when parsing broken borders

There was an infinite loop when parsing invalid text after having parsed
a color in the border shorthand. See attached testcase for an example.
css: Fail animation shorthand parsing properly

When a number is not a nubmer, don't just crash, exit properly with an
error code.

See attached testcase for an example.
GDK W32: support font scaling

Respect system font scaling (Control Panel -> Display -> Font Size) and
convey that information to GDK (which then passes it to Pango).

https://bugzilla.gnome.org/show_bug.cgi?id=734038
GDK W32: add environment variable to override system font scaling

Support environment variable GDK_WIN32_FONT_RESOLUTION that can be set to
a desired dpi (72, 96, 130, etc) to override system settings. Useful for
debugging, since changing system font scaling requires the user to log off
and log on again.

https://bugzilla.gnome.org/show_bug.cgi?id=734038
label: Don't clip text shadows

The previous code for computing the clip rectangle forgot to respect
the text-shadow CSS property. This is usually not very visible because
text shadows usually don't extend the ink rectangle by very much.

See attached testcase for an example.
Updated POTFILES.skip
textiter: don't call g_utf8_prev_char() on start of string

Changes also the "goto finally" with a break. A break is more common.

Another way is to use g_utf8_find_prev_char().

https://bugzilla.gnome.org/show_bug.cgi?id=638709