MFC r261283:

MFC r261283:

Import libc++ 3.4 release.  This contains a lot of bugfixes, and some
preliminary support for C++1y.

MFC r261604:

HEAD is not buildable for the past day.  Commit a 'quick fix' in order to permit
buildworld to complete.

Reviewed by:	theraven

MFC r261608:

Apply a cleaner solution for the sign warnings that can occur when
compiling libc++'s <locale> header with -Wsystem-headers on.

This has also been submitted upstream.

Reported by:	asomers

MFC r261801:

An ABI incompatibility crept into the libc++ 3.4 import in r261283.  It
was caused by upstream libc++ commit r194536, which aimed to make the
headers more standards-compliant, by making std::pair's copy constructor
trivial.  Unfortunately, this could cause certain C++ applications using
shared libraries built against the previous version of libc++ to crash.

Fix the ABI incompatibility by making std::pair's copy constructor
non-trivial again.

Please note: Any C++ applications or shared libraries built with libc++
between r261283 and this revision should be recompiled.

Reported by:	stefanf

git-svn-id: svn://svn.freebsd.org/base/stable/10@262801 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f