Defstruct default values

[Rob MacLachlan <RAM@>]

I propose the following "clarification":

    The default value for a defstruct slot need not be of the type
    indicated in the :type slot option as long as the default is never
    used. 

This is obviously semantically barfucious, but is essential for anyone
who ever actually uses the :type option, since there is no way to
specify a type without specifiying a default.  In many cases it is
incredibly difficult to come up with a default expression that you
can type in which will evaluate to an object of the correct type.  I
have better things to do with my time than write hairy code which is
never evaluated.

  Rob