python3.7 requires Visual Studio 2017

[anthrotype]

I just tried to run py -3.7 setup.py bdist_wheel --static-deps on Windows 10 machine running the latest python 3.7.0 and I got an error saying that

The object or library file 'libs\iconv-1.14.win64\lib\iconv_a.lib' was created with an older compiler than other objects; rebuild old objects and libraries

I noticed that the buildlibxml.py script included in the lxml repository downloads the precompiled binaries to include in the lxml windows wheels for python3.5 and 3.6 from this github repository.

So I guess the next step in order to have lxml python3.7 wheels for Windows is to update this to make available static libraries of libxml2, libxslt, zlib and iconv that are compiled with the latest Visual Studio 2017.