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 r251820. This fixes some symbol visibility issues with libsupc++ that broke
compilation of GNUstep libobjc.

MFC r246028 (by theraven):

Fix some symbol version mismatches between libstdc++ and libsupc++/libcxxrt
that were causing the runtime and STL libraries to see different versions of
various classes and functions when libstdc++ is used as a filter.

Note: This changes the ABI for libcxxrt, but libcxxrt is currently only in
-STABLE for testing and is not used by anything unless explicitly enabled by
the end user. No default compiler configurations use it.

libc++ will need to be recompiled after this change. make buildworld will do
this automatically, but make in lib/libc++ will not necessarily work unless the
new libcxxrt is installed first.

PR: kern/171610, stand/175453
Reviewed by: kib

MFC r246297:

Add several missing symbols to libcxxrt's symbol version map, and remove
a few duplicates. This should fix building world with -stdlib=libc++
after r246028.

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

MFC symbol exports for libsupcc++ and libcxxrt that correctly export new and
delete operators.

Merge r233749, building libsupc++ as a shared library and making libstdc++ a
filter library.

It should now be possible to build applications on 9-STABLE that link against
both libc++ and libstdc++ and to test libcxxrt with libstdc++.

If you wish to test libcxxrt, please add this to your /etc/libmap.conf:

libsupc++.so.1 libcxxrt.so.1

If you wish to test libc++, add -std=libc++ to your compile and link flags for
your favourite C++ applications and / or libraries.

Make libsupc++ build as a shared library and make libstdc++ a filter library
for it.

This allows people to swap out libsupc++ for libcxxrt easily, so we can begin
the libstdc++ -> libc++ migration.

Approved by: dim (mentor)

This commit was generated by cvs2svn to compensate for changes in r169691,
which included commits to RCS files with non-trunk default branches.

GCC 4.2.0 release C++ standard library and runtime support code.