Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r253917:

After r253839, which modifies ld's behaviour to not automatically pull
in needed libraries, change libc++.so into a linker script, so it can
automatically pull in libcxxrt.so.

[Note to stable/9 users: the above statement about ld's behaviour is not
(yet) applicable to the version of ld in 9.x, but this change will help
when building C++ programs with libc++, in combination with the ports
version of ld.]

MFC r242472:

Fix broken macro checking in the libc++ Makefile, introduced in r241909.
This caused -std=c++0x not to be passed to the build by default.

Pointy hat to: dim

MFC r241909:

Allow building libc++ with any custom -std=xxx flag. Note that using
-std=gnu++98 will give a lot of warnings with clang, so please use
-std=c++0x or higher, or use NO_WERROR.

MFC r239680:

Add libcxxrt's objects (prefixing them with cxxrt_ to avoid collisions)
to libc++.a and libc++_p.a, to make static linking of C++ executables
with libc++ easier. This is similar to the approach used in libstdc++.

MFC r239686:

When using -stdlib=libc++, add the correct dependency to .depend in
bsd.prog.mk.

Submitted by: Yamaya Takashi <yamayan@kbh.biglobe.ne.jp>

MFC r239695:

For building libstdc++ and libsupc++, filter out any -stdlib=libc++
option from CXXFLAGS, otherwise these libraries will not build.
Similarly, filter out any -std=xxx options that aren't supported.

Submitted by: Yamaya Takashi <yamayan@kbh.biglobe.ne.jp>

MFC r236444:

Install libcxxrt's C++ ABI and unwind headers. This is done in libc++'s
Makefile, so these headers go into the same destination directory as
libc++'s own headers, currently /usr/include/c++/v1.

MFC r236442:

Tabify libcxxrt and libc++'s Makefiles.

Merged libcxxrt and libc++. Now available for testing on 9-stable with
-stdlib=libc++. Changes to libstdc++ not yet merged, so it is not yet possible
to mix libstdc++ and libc++ in the same program.

Merged revisions: 226702,226785,227006,227755,227983,227987,228531,228630,228761,229067,230127,232950,233098,234715-234716,234772

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)