Backport into build-201006221614-5.1.46sp1

> ------------------------------------------------------------
> revno: 3351.47.2
> revision-id: marko.makela@oracle.com-20100511104910-nim8kgguawpis7zo
> parent: marko.makela@oracle.com-20100511104500-c6kzd0bg5s42p8e9
> committer: Marko Mäkelä <marko.makela@oracle.com>
> branch nick: mysql-5.1-innodb2
> timestamp: Tue 2010-05-11 13:49:10 +0300
> message:
>   btr_page_split_and_insert(): Add an assertion
>   suggested by Sunny Bains when reviewing Bug #52964.

storage/innodb_plugin/btr/btr0btr.c

@@ -2004,6 +2004,7 @@ func_start:
 			goto insert_empty;
 		}
 	} else if (UNIV_UNLIKELY(insert_left)) {
+		ut_a(n_iterations > 0);
 		first_rec = page_rec_get_next(page_get_infimum_rec(page));
 		move_limit = page_rec_get_next(btr_cur_get_rec(cursor));
 	} else {