patch 8.2.3967: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more errors to errors.h.
diff --git a/src/gui_gtk_x11.c b/src/gui_gtk_x11.c
index ba3993b..acd36d3 100644
--- a/src/gui_gtk_x11.c
+++ b/src/gui_gtk_x11.c
@@ -1507,7 +1507,7 @@
     {
 	gui.dying = TRUE;
 	if (give_message)
-	    emsg(_((char *)e_opendisp));
+	    emsg(_((char *)e_cannot_open_display));
 	return FAIL;
     }
     return OK;
@@ -1553,7 +1553,7 @@
     if (!gtk_init_check(&gui_argc, &gui_argv))
     {
 	gui.dying = TRUE;
-	emsg(_((char *)e_opendisp));
+	emsg(_((char *)e_cannot_open_display));
 	return FAIL;
     }