Make g_test_expect_message work for structured logs
Make g_test_expect_message work for structured logs

This is used in GTK+ tests, and GTK+ has switched to
G_LOG_USE_STRUCTURED, so we need this to keep working.

johne53/MB3Glib,endlessm/glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib