* testsuite/26_numerics/slice_array_assignment.cc (main): New test.

        * include/bits/slice_array.h (slice_array<>::operator=): Make
        public and implement.
        (slice_array<>::slice_array): Make copy-constructor public.

        * include/bits/valarray_array.h (__valarray_copy): Add another
        overload to copy between strided arrays.

From-SVN: r43352