MSVC iso646.h conflict in boost/python/operators.hpp

MSVC includes iso646.h under various circumstances, which is easily worked around and is actually seen elsewhere in MPL (Boost issue https://svn.boost.org/trac/boost/ticket/3018). This applies strictly to MSVC, and when iso646.h is included from various means. The trac specifically said use github for Boost.Python related issues, so here I am.

iso646.h defines various bitwise macros which are conflicting with the python operators (or, and, xor).

This is easily fixed with prefix/postfix push_macro and pop_macro's for the appropriate functions.

I have attached a diff against 1.61.

[operators.patch.txt](https://github.com/boostorg/python/files/267087/operators.patch.txt)

Start in boost/python/operators.hpp and compare the attached operators.patch.txt against the current implementation. Reproduce the issue with MSVC when iso646.h is included, then verify that the conflicting operator macros no longer break compilation.

Escrita pelo modelo de indexação a partir do texto da issue.