patch 8.0.0466: still macros that should be all-caps

Problem:    There are still a few macros that should be all-caps.
Solution:   Make a few more macros all-caps.
diff --git a/src/buffer.c b/src/buffer.c
index ca3be14..83d74a3 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -6021,7 +6021,7 @@
 	if (buf->b_signlist != NULL)
 	{
 	    vim_snprintf(lbuf, BUFSIZ, _("Signs for %s:"), buf->b_fname);
-	    MSG_PUTS_ATTR(lbuf, hl_attr(HLF_D));
+	    MSG_PUTS_ATTR(lbuf, HL_ATTR(HLF_D));
 	    msg_putchar('\n');
 	}
 	for (p = buf->b_signlist; p != NULL && !got_int; p = p->next)