Developer credits
Git commits in Moodle 3.1.12 by Tim Hunt
commit b7bbe9fd9466036a84fe7bc4619b376f05b7049f Author: Tim Hunt <T.J.Hunt@open.ac.uk> Date: Tue, 01 May 2018 02:45:47 +0800 Tag: v3.1.12 MDL-62275 qtype_calc*: improve validation of formulae