message: Require newest CMake nightly on MSVC
  This replaces the VS2017 /std:c++17 workaround.
diff: cmake_minimum_required(VERSION 3.1.3)
  project(eos)
  +if(MSVC)
  + cmake_minimum_required(VERSION 3.9.20170812-g71ee6) # needed for CMAKE_CXX_STANDARD 17
  +endif()
  set(eos_VERSION_MAJOR 0)
  set(eos_VERSION_MINOR 12)
  set(eos_VERSION_PATCH 1)
  @@ -106,9 +109,6 @@ set(HEADERS
  add_library(eos INTERFACE)
  target_compile_features(eos INTERFACE ${EOS_CXX_COMPILE_FEATURES})
  -# Add c++17 flag for VS2017:
  -# Results in a warning that both /std:c++14 and c++17 are defined but we can't get around that until CMake properly supports it.
  -target_compile_options(eos INTERFACE "$<$<CXX_COMPILER_ID:MSVC>:/std:c++17>")
  # Add header includes:
  target_include_directories(eos INTERFACE "include")
  