Synchronize the default C++ stack in stable/10 with head, by merging

Synchronize the default C++ stack in stable/10 with head, by merging
almost all recent changes to libc++ and libcxxrt.

MFC r256642:
  Since C++ typeinfo objects are currently not guaranteed to be merged at
  runtime by the dynamic linker, check for their equality in libcxxrt by
  not only comparing the typeinfo's name pointers, but also comparing the
  full names, if necessary.  (This is similar to what GNU libstdc++ does
  in its default configuration.)  The 'deep' check can be turned off again
  by defining LIBCXXRT_MERGED_TYPEINFO, and recompiling libcxxrt.

  Reviewed by:	theraven

MFC r270522 (by rdivacky):
  The standard we compile libc++ with is called c++11 not c++0x.

MFC r273066 (by bapt):
  Import patch from libc++ r197313 which allows using libc++ headers with gcc

  Differential Revision:	https://reviews.freebsd.org/D942
  Reviewed by:	imp

MFC r273381 (by bapt):
  Add support for __cxa_throw_bad_array_new_length in libcxxrt

  It is required for use with newer g++49

  Differential Revision:	https://reviews.freebsd.org/D982
  Reviewed by:	theraven
  Approved by:	theraven

MFC r273382 (by bapt):
  Fix build by marking the new functions as weak
  This is a temporary fix

MFC r273407 (by bapt):
  When using an external gcc 4.8+ and not building libstdc++ then create in the objectdir a
  fake libstdc++.so and libstdc++.a which is a symlink on libc++ that allow g++ to satisfy
  its links dependencies in the least hackish way.
  Please note that this hacky libstds++ never get installed on the final system

  Reviewed by:	imp

MFC r273434 (by bapt):
  Do not define bad_array_new_length::bad_array_new_length in libc++ anymore
  when used in combinaison with libcxxrt since it is now defined there already.
  This fixes building world

MFC r276417:
  Import libcxxrt master 00bc29eb6513624824a6d7db2ebc768a4216a604.

  Interesting fixes:
  76584a0  Reorganize code to use only 32bit atomic ops for 32bit platforms
  30d2ae5  Implement __cxa_throw_bad_array_new_length

  Reviewed by:	bapt
  Differential Revision: https://reviews.freebsd.org/D1390

MFC r277217:
  Import libc++ trunk r224926.  This fixes a number of bugs, completes
  C++14 support[1], adds more C++1z features[2], and fixes the following
  LWG issues[3]:

  1450: Contradiction in regex_constants
  2003: String exception inconsistency in erase.
  2075: Progress guarantees, lock-free property, and scheduling
	assumptions
  2104: unique_lock move-assignment should not be noexcept
  2112: User-defined classes that cannot be derived from
  2132: std::function ambiguity
  2135: Unclear requirement for exceptions thrown in
	condition_variable::wait()
  2142: packaged_task::operator() synchronization too broad?
  2182: Container::[const_]reference types are misleadingly specified
  2186: Incomplete action on async/launch::deferred
  2188: Reverse iterator does not fully support targets that overload
	operator&
  2193: Default constructors for standard library containers are explicit
  2205: Problematic postconditions of regex_match and regex_search
  2213: Return value of std::regex_replace
  2240: Probable misuse of term "function scope" in [thread.condition]
  2252: Strong guarantee on vector::push_back() still broken with C++11?
  2257: Simplify container requirements with the new algorithms
  2258: a.erase(q1, q2) unable to directly return q2
  2263: Comparing iterators and allocator pointers with different
	const-character
  2268: Setting a default argument in the declaration of a member
	function assign of std::basic_string
  2271: regex_traits::lookup_classname specification unclear
  2272: quoted should use char_traits::eq for character comparison
  2278: User-defined literals for Standard Library types
  2280: begin / end for arrays should be constexpr and noexcept
  2285: make_reverse_iterator
  2288: Inconsistent requirements for shared mutexes
  2291: std::hash is vulnerable to collision DoS attack
  2293: Wrong facet used by num_put::do_put
  2299: Effects of inaccessible key_compare::is_transparent type are not
	clear
  2301: Why is std::tie not constexpr?
  2304: Complexity of count in unordered associative containers
  2306: match_results::reference should be value_type&, not const
	value_type&
  2308: Clarify container destructor requirements w.r.t. std::array
  2313: tuple_size should always derive from integral_constant<size_t, N>
  2314: apply() should return decltype(auto) and use decay_t before
	tuple_size
  2315: weak_ptr should be movable
  2316: weak_ptr::lock() should be atomic
  2317: The type property queries should be UnaryTypeTraits returning
	size_t
  2320: select_on_container_copy_construction() takes allocators, not
	containers
  2322: Associative(initializer_list, stuff) constructors are
	underspecified
  2323: vector::resize(n, t)'s specification should be simplified
  2324: Insert iterator constructors should use addressof()
  2329: regex_match()/regex_search() with match_results should forbid
	temporary strings
  2330: regex("meow", regex::icase) is technically forbidden but should
	be permitted
  2332: regex_iterator/regex_token_iterator should forbid temporary
	regexes
  2339: Wording issue in nth_element
  2341: Inconsistency between basic_ostream::seekp(pos) and
	basic_ostream::seekp(off, dir)
  2344: quoted()'s interaction with padding is unclear
  2346: integral_constant's member functions should be marked noexcept
  2350: min, max, and minmax should be constexpr
  2356: Stability of erasure in unordered associative containers
  2357: Remaining "Assignable" requirement
  2359: How does regex_constants::nosubs affect basic_regex::mark_count()?
  2360: reverse_iterator::operator*() is unimplementable

  [1] http://libcxx.llvm.org/cxx1y_status.html
  [2] http://libcxx.llvm.org/cxx1z_status.html
  [3] http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html

  Exp-run:	antoine

MFC r277944:
  Partially revert r273382, to reduce diffs against upstream.  This was a
  temporary fix to solve a conflict with an older version of libc++, and
  it is no longer relevant.

MFC r278010:
  Revert r256642, not only to reduce diffs against upstream libcxxrt, but
  also because it is the wrong approach: comparing typeinfo names deeply
  causes trouble if two loaded DSOs use independent types of the same
  name.

  In addition, this particular change was never merged to FreeBSD 10.x and
  9.x, so let's get rid of it before it ends up in an 11.x release.

  Discussed with:	theraven, joerg@netbsd

MFC r278016:
  Import libcxxrt master 1cb607e89f6135bbc10f3d3b6fba1f983e258dcc.

  Interesting fixes:
  1cb607e Correct gcc version check for __cxa_begin_catch() declaration
          with or without throw()

git-svn-id: svn://svn.freebsd.org/base/stable/10@278724 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f