Add libc++ and libc++abi to third-party.

third_party/libcxx/include/__sso_allocator

Index: third_party/libcxx/include/__sso_allocator
===================================================================
--- third_party/libcxx/include/__sso_allocator	(revision 0)
+++ third_party/libcxx/include/__sso_allocator	(revision 0)
@@ -0,0 +1,77 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___SSO_ALLOCATOR
+#define _LIBCPP___SSO_ALLOCATOR
+
+#include <__config>
+#include <type_traits>
+#include <new>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Tp, size_t _Np> class _LIBCPP_HIDDEN __sso_allocator;
+
+template <size_t _Np>
+class _LIBCPP_HIDDEN __sso_allocator<void, _Np>
+{
+public:
+    typedef const void*       const_pointer;
+    typedef void              value_type;
+};
+
+template <class _Tp, size_t _Np>
+class _LIBCPP_HIDDEN __sso_allocator
+{
+    typename aligned_storage<sizeof(_Tp) * _Np>::type buf_;
+    bool __allocated_;
+public:
+    typedef size_t            size_type;
+    typedef _Tp*              pointer;
+    typedef _Tp               value_type;
+
+    _LIBCPP_INLINE_VISIBILITY __sso_allocator() throw() : __allocated_(false) {}
+    _LIBCPP_INLINE_VISIBILITY __sso_allocator(const __sso_allocator&) throw() : __allocated_(false) {}
+    template <class _Up> _LIBCPP_INLINE_VISIBILITY __sso_allocator(const __sso_allocator<_Up, _Np>&) throw()
+         : __allocated_(false) {}
+private:
+    __sso_allocator& operator=(const __sso_allocator&);
+public:
+    _LIBCPP_INLINE_VISIBILITY pointer allocate(size_type __n, typename __sso_allocator<void, _Np>::const_pointer = 0)
+    {
+        if (!__allocated_ && __n <= _Np)
+        {
+            __allocated_ = true;
+            return (pointer)&buf_;
+        }
+        return static_cast<pointer>(::operator new(__n * sizeof(_Tp)));
+    }
+    _LIBCPP_INLINE_VISIBILITY void deallocate(pointer __p, size_type)
+    {
+        if (__p == (pointer)&buf_)
+            __allocated_ = false;
+        else
+            ::operator delete(__p);
+    }
+    _LIBCPP_INLINE_VISIBILITY size_type max_size() const throw() {return size_type(~0) / sizeof(_Tp);}
+
+    _LIBCPP_INLINE_VISIBILITY
+    bool operator==(__sso_allocator& __a) const {return &buf_ == &__a.buf_;}
+    _LIBCPP_INLINE_VISIBILITY
+    bool operator!=(__sso_allocator& __a) const {return &buf_ != &__a.buf_;}
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif  // _LIBCPP___SSO_ALLOCATOR