VSIPL16 — VSIPL++ spec references nonexistent complex types

The specification defines complex_i as "The implementation shall define
this type to be complex<short>, complex<int>, or complex<long int> such
that the choice of underlying type is the same as scalar_i."

This is problematic, because the C++ spec states that complex<T> is not
necessarily defined when T is not float or double. In practice, GCC
provides only incomplete definitions for the int/short/long cases.

Since cscalar_i is only used in a very few places, I suggest that it
should simply be removed from the spec.

(The changelog in the back of the document mentions a change related to
this, but the actual text does not appear to be changed.)