Previously, Initial Setup would only change the LC_MESSAGES locale
category when the user selects a different locale on the language page.
However, this caused non-ASCII characters to be mangled after switching
locale. The following test program demonstrates the problem:

    #include "config.h"
    #include <locale.h>
    #include <glib.h>
    #include <glib/gi18n-lib.h>
    #include <libgweather/gweather.h>

    gint
    main (gint   argc,
          gchar *argv[])
    {
      /* gettext boilerplate */
      setlocale (LC_ALL, "");
      bindtextdomain (GETTEXT_PACKAGE, GNOMELOCALEDIR);
      bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
      textdomain (GETTEXT_PACKAGE);

      /* Change locale to Czech */
      locale_t locale = newlocale (LC_MESSAGES_MASK, "cs_CZ.utf8", (locale_t) 0);
      g_assert (locale != (locale_t) 0);
      uselocale (locale);

      GWeatherLocation *world = gweather_location_get_world ();
      GWeatherLocation *praha = g...