We want to set _WIN32_WINNT so that functions will be properly found in
the headers, to target the NT6.1+ (Windows 7+) APIs.
Also improve the checks for if_nametoindex() and if_indextoname() on
Windows as they are supported in Windows Vista+, but they have
to be checked by linking against iphlpapi.lib (or -liphlpapi). On other
platforms, they are still checked as they were before.
https://bugzilla.gnome.org/show_bug.cgi?id=783270
Disable gio tests on Windows, fix .gitignore to not ignore
config.h.meson, and add more things to it.
Rename the library file naming and versioning to match what Autotools
outputs, e.g., libglib-2.0.so.0.5000.2 on Linux, libglib-2.0-0.dll and
glib-2.0-0.dll on Windows with MSVC.
Several more tiny fixes, more executables built and installed, install
pkg-config and m4 files, fix building of gobject tests.
Changes to gdbus-codegen to support out-of-tree builds without
environment variables set (which you can't in Meson). We now add the
build directory to the Python module search path.
