Fix to issue #789.

backup/moodle2/backup_qtype_stack_plugin.class.php

db/install.xml

db/upgrade.php

doc/en/Authoring/Options.md

doc/en/Authoring/Testing.md

edit_stack_form.php

lang/en/qtype_stack.php

questiontype.php

samplequestions/equivalence_reasoning_example.xml

samplequestions/file_download.xml

...uestions/stack-js/stack-js-issue-specific-example-938.xml

settings.php

stack/cas/ast.container.class.php

stack/maxima/stackmaxima.mac

stack/options.class.php

stack/questiontest.php

tests/helper.php

tests/questiontype_test.php

version.php