Git commits in Moodle 2.3.x by Matt Petro

commit c8b33aa772aeda566c6f43892c0e46c131dd6a3c
Author: Matt Petro <petro@engr.wisc.edu>
Date:   Tue, 16 Apr 2013 19:19:23 +0800
Tag:    v2.3.7

MDL-34403 mod quiz: fix error during enrolment

commit 2cae75aacc0f1829aa957228e95a6033fc8f2caf
Author: Matt Petro <petro@engr.wisc.edu>
Date:   Fri, 19 Oct 2012 22:59:42 +0800
Tag:    v2.3.4

MDL-36025 qtype calculated: Fix handling of "-0"

commit 30ef79639cebdb091cd534e6cb5447d00f3f049b
Author: Matt Petro <petro@engr.wisc.edu>
Date:   Wed, 10 Oct 2012 01:48:30 +0800
Tag:    v2.3.4

MDL-35717 quiz: fix overdue attempt processing