Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Import new libcxxrt / libc++. This brings some bug fixes, including a potential race condition for static initialisers.

Merge libc++ trunk r180598. Contains several minor cleanups and bug
fixes, no major changes.

MFC after: 2 weeks

Import new libc++ to head. Various small fixes and cleanups.

MFC after: 2 weeks

Import libc++ trunk r165949. Among other improvements and bug fixes,
this has many visibility problems fixed, which should help with
compiling certain ports that exercise C++11 mode (i.e. Firefox).

Also, belatedly add the LICENSE.TXT and accompanying CREDITS.TXT files,
which are referred to in all the source files.

MFC after: 1 month

Import new versions of libcxxrt and libc++.
Please tests any C++ code you care about with -stdlib=libc++!

Approved by: dim (mentor)

Import libc++ / libcxxrt into base. Not build by default yet (use
MK_LIBCPLUSPLUS=yes to enable). This is a work-in-progress. It works for
me, but is not guaranteed to work for anyone else and may eat your dog.

To build C++ using libc++, add -stdlib=libc++ to your CXX and LD flags.

Bug reports welcome, bug fixes even more welcome...

Approved by: dim (mentor)

Import libcxxrt / libc++ into a vendor branch.

Approved by: dim (mentor)