patch 8.1.0753: printf format not checked for semsg()

Problem:    printf format not checked for semsg().
Solution:   Add GNUC attribute and fix reported problems. (Dominique Pelle,
            closes #3805)
diff --git a/src/netbeans.c b/src/netbeans.c
index eb61b31..65b2f70 100644
--- a/src/netbeans.c
+++ b/src/netbeans.c
@@ -1541,7 +1541,7 @@
 		if (!buf->bufp->b_netbeans_file)
 		{
 		    nbdebug(("E658: NetBeans connection lost for buffer %ld\n", buf->bufp->b_fnum));
-		    semsg(_("E658: NetBeans connection lost for buffer %ld"),
+		    semsg(_("E658: NetBeans connection lost for buffer %d"),
 							   buf->bufp->b_fnum);
 		}
 		else