MSVC builds: Update how introspection builds are done

MSVC builds: Update how introspection builds are done

This first adds a common autotools module that can be included by
the Makefile.am's to generate the file lists and the g-ir-scanner/
g-ir-compiler command lines to build the introspection files.

The autotools files for gdk/ and gtk/ are then updated to generate
the full file lists needed to build the introspection files, with
the full command lines for g-ir-scanner and g-ir-compiler as NMake
Makefile modules that can be used to build the introspection files
for Visual Studio builds.

https://bugzilla.gnome.org/show_bug.cgi?id=765195