This updates the Visual Studio Project GUIDs so that they don't repeat with
the GTK+-2.24.x ones, as the 3.x projects can be used with the 2.24.x in a
all-in-one solution file (such as when one wants to use a complete GTK+2
and GTK+3 stack when porting Windows applications from GTK+2 to GTK+3), and
each project in a solution file is expected to have an unique GUID.
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.
