[atkmm] (6 commits) Non-fast-forward update to branch master.nmake

[Chun-wei Fan <fanchunwei src gnome org>]

The branch 'master.nmake' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  b60c632... build: Rename MSVC_Net2017 to MSVC_NMake
  b1664fc... build: Split out GNU-specific syntax from atk/atkmm/filelis
  1cd9645... build: Add NMake Makefiles for Visual Studio builds
  98b9aab... build: Remove the Visual Studio 2017 projects

Commits added to the branch:

  67c7de9... Use glibmm-2.58 instead of glibmm-2.56 (*)
  b626bc5... Require C++17 (*)
  adcec2a... build: Rename MSVC_Net2017 to MSVC_NMake
  6e364a4... build: Split out GNU-specific syntax from atk/atkmm/filelis
  17385b9... build: Add NMake Makefiles for Visual Studio builds
  981fac9... build: Remove the Visual Studio 2017 projects

(*) This commit already existed in another branch; no separate mail sent