This was one of those innocent seeming issues where, once you start
digging, you find a mess. In this case, the code that is now in
question_wizard_form::add_hidden_fields used to exist in four different
places, in four inconsistent versions. This is now all nicely
re-factored, and that solves the problem.
Along the way, I found and fixed some wrong string references in
qtype_random, and stripped out some unnecessary &s in function
declarations.
Tim Hunt
d4d8a51fae