The <algorithm> header includes <utility>, with a comment referring to
UK-300, a National Body comment on the C++11 draft. That comment
proposed to move std::swap to <utility> and then require <algorithm> to
include <utility>. The comment was rejected, so we do not need to
implement the suggestion. For backwards compatibility with C++03 we do
want <algorithm> to define std::swap, but it does so anyway via
<bits/move.h>. We don't need the whole of <utility> to do that.

A few other headers that need std::swap can include <bits/move.h> to
get it, instead of <utility>.

There are several headers that include <utility> to get std::pair, but
they can use <bits/stl_pair.h> to get it without also including the
rel_ops namespace and other contents of <utility>.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

         * include/std/algorithm: Do not include <utility>.
         * include/std/functional: Likewise.
         * include/std/regex: Include <bits/stl_pair.h> instead of
         <utility>.
         * include/debug/map.h: Likewise.
         * include/debug/multimap.h: Likewise.
         * include/debug/multiset.h: Likewise.
         * include/debug/set.h: Likewise.
         * include/debug/vector: Likewise.
         * include/bits/fs_path.h: Likewise.
         * include/bits/unique_ptr.h: Do not include <utility>.
         * include/experimental/any: Likewise.
         * include/experimental/executor: Likewise.
         * include/experimental/memory: Likewise.
         * include/experimental/optional: Likewise.
         * include/experimental/socket: Use __exchange instead
         of std::exchange.
         * src/filesystem/ops-common.h: Likewise.
         * testsuite/20_util/default_delete/48631_neg.cc: Adjust expected
         errors to not use a hardcoded line number.
         * testsuite/20_util/default_delete/void_neg.cc: Likewise.
         * testsuite/20_util/specialized_algorithms/uninitialized_copy/constrained.cc:
         Include <utility> for std::as_const.
         * testsuite/20_util/specialized_algorithms/uninitialized_default_construct/constrained.cc:
         Likewise.
         * testsuite/20_util/specialized_algorithms/uninitialized_move/constrained.cc:
         Likewise.
         * testsuite/20_util/specialized_algorithms/uninitialized_value_construct/constrained.cc:
         Likewise.
         * testsuite/23_containers/vector/cons/destructible_debug_neg.cc:
         Adjust dg-error line number.


Tested powerpc64le-linux. Committed to trunk.