1.0.36.6: array data vector type derivation

1.0.36.6: array data vector type derivation

 * Needs to be done for ARRAY-STORAGE-VECTOR and %ARRAY-DATA-VECTOR
   in addition to %DATA-VECTOR-AND-INDEX.

 * If the array is simple, we may be able to derive the exact length
   of the data vector, not just the element type.