Build failure MSVC 14 (x86) on Boost 1.68.0

Hi,

After upgrading to Boost 1.68.0, builds using lockfree fail on x86; x64 works.

Compiler version:

Microsoft (R) C/C++ Optimizing Compiler Version 19.00.24215.1 for x86
Copyright (C) Microsoft Corporation. All rights reserved.

On trying to compile the test cases, I get this error (complete log attached):
```
stack_bounded_stress_test.cpp
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(508): error C2719: '_Val': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(669): note: see reference to class template instantiation 'std::_Atomic_base<_Ty,8>' being compiled
with
[
_Ty=boost::lockfree::detail::tagged_ptr::node,std::allocator::node>>::freelist_node>
]
T:\boost_1_68_0\boost/lockfree/detail/freelist.hpp(255): note: see reference to class template instantiation 'std::atomic::freelist_node>>' being compiled
with
[
T=boost::lockfree::stack::node,
Alloc=std::allocator::node>
]
T:\boost_1_68_0\boost/lockfree/stack.hpp(100): note: see reference to class template instantiation 'boost::lockfree::detail::freelist_stack' being compiled
with
[
T=boost::lockfree::stack::node,
Alloc=std::allocator::node>
]
stack_bounded_stress_test.cpp(25): note: see reference to class template instantiation 'boost::lockfree::stack' being compiled
T:\boost_1_68_0\boost/bind/placeholders.hpp(54): note: see reference to class template instantiation 'boost::arg<9>' being compiled
T:\boost_1_68_0\boost/bind/placeholders.hpp(53): note: see reference to class template instantiation 'boost::arg<8>' being compiled
T:\boost_1_68_0\boost/bind/placeholders.hpp(52): note: see reference to class template instantiation 'boost::arg<7>' being compiled
T:\boost_1_68_0\boost/bind/placeholders.hpp(51): note: see reference to class template instantiation 'boost::arg<6>' being compiled
T:\boost_1_68_0\boost/bind/placeholders.hpp(50): note: see reference to class template instantiation 'boost::arg<5>' being compiled
T:\boost_1_68_0\boost/bind/placeholders.hpp(49): note: see reference to class template instantiation 'boost::arg<4>' being compiled
T:\boost_1_68_0\boost/bind/placeholders.hpp(48): note: see reference to class template instantiation 'boost::arg<3>' being compiled
T:\boost_1_68_0\boost/bind/placeholders.hpp(47): note: see reference to class template instantiation 'boost::arg<2>' being compiled
T:\boost_1_68_0\boost/bind/placeholders.hpp(46): note: see reference to class template instantiation 'boost::arg<1>' being compiled
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(519): error C2719: '_Right': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(525): error C2719: '_Right': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(542): error C2719: '_Value': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(548): error C2719: '_Value': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(580): error C2719: '_Value': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(587): error C2719: '_Value': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(594): error C2719: '_Value': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(602): error C2719: '_Value': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(610): error C2719: '_Value': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(617): error C2719: '_Value': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(624): error C2719: '_Value': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(632): error C2719: '_Value': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(640): error C2719: '_Value': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(647): error C2719: '_Value': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(680): error C2719: '_Val': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(686): error C2719: '_Right': formal parameter with requested alignment of 8 won't be aligned
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\atomic(691): error C2719: '_Right': formal parameter with requested alignment of 8 won't be aligned
```

Could you please have a look on how to fix this issue?

[Complete log](https://github.com/boostorg/lockfree/files/2322722/output.log)

Start by reproducing the x86 MSVC 14 build of stack_bounded_stress_test.cpp and review the atomic instantiation shown through boost/lockfree/detail/freelist.hpp and boost/lockfree/stack.hpp. Use the attached output.log to compare the failing x86 build with x64; done means the lockfree test cases compile successfully on x86 without regressing x64.

Written by the indexing model from the issue text.