valarray_after.h (_Expr<>::operator[](slice)): Don't assume the closure implements...

valarray_after.h (_Expr<>::operator[](slice)): Don't assume the closure implements general indexing...

        * include/bits/valarray_after.h (_Expr<>::operator[](slice)):
        Don't assume the closure implements general indexing, as a matter
        of fact, most of them don't.
        (_Expr<>::operator[](const gslice&)): Likewise.
        (_Expr<>::operator[](const valarray<bool>&)): Likewise.
        (_Expr<>::operator[](const valarray<size_t>&)): Likewise.
        (_Expr<>::shift): Fix thinko.
        (_Expr<>::cshift): Likewise.
        (_Expr<>::apply): Likewise.

From-SVN: r108714