Combine repetitive parts, and unify using $(PythonDir) for all builds,
which the paths set in the property sheets are now based on the Visual
Studio version and platform combination.
This is so that it is easier for one building GTK+ with Visual Studio to
build the introspection files as well in one shot. Note that this is
not built by default, so one needs to select the gtk3-introspect
explicitly to build (and clean up) the introspection files.
For this to work, one needs to ensure the following:
-A complete build of GObject-Introspection in $(GlibEtcInstallRoot),
that is built with the same installation of the Python interpretor that
is used here (see PythonDir and PythonDirX64 in
gtk3-version-paths.[vsprops|props]).
-Introspection files for ATK, GDK-Pixbuf and Pango, also in their proper
locations under $(GlibEtcInstallRoot), which should be built with the
same G-I installation.
This is to make this more in-line with what is in the G-I projects, so
that we could use this to build the introspection files for GTK+-3.22.x
directly from the project files. This is intended to follow the MSVC
versions used to build the official CPython Windows binaries, i.e.:
-3.3.x, 3.4.x: for MSVC 2010, 2012, 2013, which is built with 2010
-3.5.x, 3.6.x: for 2015 and 2017, which is built with 2015.
Generate .pc files for the package, so that it would be easier for
building introspection for packages that depend on GTK+. Also split
PythonPath into PythonPath and PythonPathX64 to facilitate the build of
introspection files, which need to have Python that is built with the
same ac=rchitecture where GTK+ is built.
Clean up the formatting and spacing a bit.
We need to rename the projects so that when these projects are added
into an all-in-one solution file that will build the GTK+ 2/3 stack,
the names of the projects will not collide with the GTK+-2.x ones,
especially as GTK+-2.x and GTK+-3.x are done to co-exist on the same
system. This is due to the case that the MSVC projects are directly
carried over from the GTK+-2.x ones and was then updated for 3.x.
We still need to update the GUIDs of the projects, so that they won't
conflict with the GTK+-2.x ones.
