Unmarshall all QVariant types which has toType conversion functions.
qvariant.lisp:
* Sort *qvariant-types* by codes.
* Make *qvariant-map* as large as needed.
* Use #'identity for invalid QVariants (with type 0).
unvariant: Don't discard unvarianted NIL.
property.lisp: Remove manual QVariant unmarshalling, since QVariant are now handled automatically.
More comprehensive QVariant marshalling.