Remove instantiations when no concept check

[Jonathan Wakely]

On 09/11/15 22:14 +0100, François Dumont wrote:
>Hi
>
>    I just committed this trivial cleanup.
>
>2015-11-09  François Dumont  <fdumont@gcc.gnu.org>
>
>    * include/bits/stl_algo.h
>    (partial_sort_copy): Instantiate std::iterator_traits only if concept
>    checks.
>    (lower_bound): Likewise.
>    (upper_bound): Likewise.
>    (equal_range): Likewise.
>    (binary_search): Likewise.
>    * include/bits/stl_heap.h (pop_heap): Likewise.

Thanks! The unused-local-typedefs warnings are quite noisy, so it's
good to get rid of them.