[l10n] Updated Italian translation.
tasks: Fix return values

https://bugzilla.gnome.org/show_bug.cgi?id=712565
core: Replace deprecated GStaticMutex with GMutex

https://bugzilla.gnome.org/show_bug.cgi?id=712565
demos: Fix GtkStock deprecated functions

https://bugzilla.gnome.org/show_bug.cgi?id=712565
Updated Belarusian translation.
core: Fix strict-aliasing problems with authentication domains

Dodgy casts are the worst.
tests: Fix strict aliasing problems with struct sockaddr

Make it a union and GCC is happy again.
core: Fix 'soup_gnome_features_2_26_get_type' is deprecated warning

GNOME 2.26 libsoup's feature was just the GNOME proxy resolver,
which is now provided as default GIO extension point.

More informations can be seen in:
[0]: https://git.gnome.org/browse/libsoup/commit/?id=4ded0924fd82e006f31a8e9089fd297fac15eef9
[1]: https://bugzilla.gnome.org/show_bug.cgi?id=573685

https://bugzilla.gnome.org/show_bug.cgi?id=712565
tests: Replace g_test_trap_fork() with g_test_trap_subprocess()

For GLib versions newer than 2.38.0. This continues to work for older
versions, so the GLib dependency is not bumped.

https://bugzilla.gnome.org/show_bug.cgi?id=712565
docs: Update libgdata website

Now: https://wiki.gnome.org/Projects/libgdata