tests: Add client helper routines for output and reference filenames

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-By: Derek Foreman <derekf@osg.samsung.com>
diff --git a/tests/weston-test-client-helper.h b/tests/weston-test-client-helper.h
index 8635471..b46f158 100644
--- a/tests/weston-test-client-helper.h
+++ b/tests/weston-test-client-helper.h
@@ -180,4 +180,10 @@
 expect_protocol_error(struct client *client,
 		      const struct wl_interface *intf, uint32_t code);
 
+char*
+screenshot_output_filename(const char *basename, uint32_t seq);
+
+char*
+screenshot_reference_filename(const char *basename, uint32_t seq);
+
 #endif