Minor update to docs.
Merge branch 'master' of github.com:maths/moodle-qtype_stack
Merge branch 'master' of github.com:maths/moodle-qtype_stack
Make /* and */ invalid fragments in casstrings to avoid partial comments ending up in the Maxima code.
Merge branch 'master' of github.com:maths/moodle-qtype_stack