patch 9.0.0620: matchaddpos() can only add up to 8 matches

Problem:    matchaddpos() can only add up to 8 matches.
Solution:   Allocate the array of positions. (closes #11248)
diff --git a/src/drawscreen.c b/src/drawscreen.c
index 4e8ef4e..4706699 100644
--- a/src/drawscreen.c
+++ b/src/drawscreen.c
@@ -1614,13 +1614,13 @@
 
 		while (cur != NULL)
 		{
-		    if (cur->match.regprog != NULL
-					   && re_multiline(cur->match.regprog))
+		    if (cur->mit_match.regprog != NULL
+				       && re_multiline(cur->mit_match.regprog))
 		    {
 			top_to_mod = TRUE;
 			break;
 		    }
-		    cur = cur->next;
+		    cur = cur->mit_next;
 		}
 	    }
 #endif