Git commits in Moodle 2.8.9 by Tim Hunt

commit fb33a080dc415db74d3e4470972d1e5ef3f0c381
Author: Tim Hunt <T.J.Hunt@open.ac.uk>
Date:   Sun, 18 Oct 2015 23:03:29 +0800
Tag:    v2.8.9

MDL-51771 question engine: fix typo in SQL

commit 58d7de73ac9640bbadb896edc0997235b5a15ebd
Author: Tim Hunt <T.J.Hunt@open.ac.uk>
Date:   Mon, 21 Sep 2015 22:12:10 +0800
Tag:    v2.8.9

MDL-51476 questions: manual grading validation for ungraded Qs

commit e8da65449a91d3a07ec8a25bd59ea3dbe934c8b6
Author: Tim Hunt <T.J.Hunt@open.ac.uk>
Date:   Fri, 18 Sep 2015 04:40:06 +0800
Tag:    v2.8.9

MDL-51375 excel output: more work to avoid invalid sheet names

commit d881f12cdee54db62c530a45e815f2564743b1aa
Author: Tim Hunt <T.J.Hunt@open.ac.uk>
Date:   Fri, 21 Aug 2015 02:12:02 +0800
Tag:    v2.8.9

MDL-51147 qtype_match: stats should cope even if Q edited badly