Without this change, out-of-tree distcheck doesn't get very far.
Similarly, allow *.vcxproj, *.props to be in either the builddir or
the srcdir.
Finally, since I'm touching these lines anyway, eliminate some
useless uses of cat: "cat x | sed 's/foo/bar/' > y" is
equivalent to "sed 's/foo/bar/' < x > y".
Bug: https://bugzilla.gnome.org/show_bug.cgi?id=748176
Reviewed-by: Chun-wei Fan <fanchunwei@src.gnome.org>
Make use of pattern rules when generating the Visual Studio 2012/2013
Projects from the Visual Studio 2010 projects, which will help to clean up
the file and also avoid problems when running items like 'make -jN dist'.
As the Visual Studio 2012/2013 are only slightly different from the Visual
Studio 2010 projects, we can provide support for them by using scripts to
copy the Visual Studio 2010 projects, and update the specific parts as
necessary.
Thus, there would be little maintenance overhead for these as only the 2010
projects need to be kept up-to-date as a result. This might change when we
do get the stack working with WinRT/Metro, but that's going to be another
totally different issue.
