Review PR #3564 so we can tag 1.4.1

Can someone please review 3564?

It fixes the fact that there were ways to get values into rcparams
that side-stepped all of the validation code which lead to some very
long standing bugs.

It raises warnings in the case of values that now fail validation, but
used to sneak in. The plan is to change the warnings to exceptions at
a later date.



Thomas Caswell