build: Update config.h.win32.in
build: Update config.h.win32.in

Update config.h.win32.in to match closely to what Meson will produce for
the various Visual Studio versions (2008~2017), as it seems that Meson
produces a better config.h for our MSVC builds of GLib.

One of the major changes in this is that all Visual Studio builds
(either through Meson, which is already so, or via the existing
projects) is that the built binaries will require Windows 7 or later,
so that we let people know early on in a cycle that MSVC builds of
2.55.0 and later will definitely need Windows 7 or later.

johne53/MB3Glib,endlessm/glib,johne53/MB3Glib,endlessm/glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,johne53/MB3Glib,endlessm/glib