display error on module window

- Currently errors are displayed on stdout. This patch puts the
error on subscreens also.
- bug 1298171

Signed-off-by: Sanjay Singh Rawat <sanjay.rawat@linaro.org>
diff --git a/display.h b/display.h
index b28d26e..e3a1529 100644
--- a/display.h
+++ b/display.h
@@ -25,6 +25,7 @@
 
 extern int display_print_line(int window, int line, char *str,
 			      int bold, void *data);
+extern void display_message(int window, char *buf);
 
 extern int display_refresh_pad(int window);
 extern int display_reset_cursor(int window);