Run accessibility tests in en_US.utf8

Previously, we were just using the C locale, which breaks
some of our fancy utf8 output for checkmarks and so on.

testsuite/a11y/accessibility-dump.c

@@ -20,6 +20,7 @@
 
 #include "config.h"
 
+#include <locale.h>
 #include <string.h>
 #include <glib/gstdio.h>
 #include <gtk/gtk.h>
@@ -874,6 +875,12 @@ parse_command_line (int *argc, char ***argv)
 
   gtk_test_init (argc, argv);
 
+  /* gtk_test_init does not call setlocale(), so do it ourselves,
+   * since running in the C locale breaks some our fancy
+   * utf8 output.
+   */
+  setlocale (LC_ALL, "en_US.utf8");
+
   return TRUE;
 }