MSVC Builds: Build gtk-encode-symbolic-svg

This utility would likely be useful for Windows builds of GTK+, given the
reasons Alex cited for coming up with this utility[1], and MSVC build
support for librsvg is not available at this time (possible, but not
implemented yet).

[1]: https://bugzilla.gnome.org/show_bug.cgi?id=730450

build/win32/vs12/Makefile.am

@@ -10,6 +10,8 @@ EXTRA_DIST +=	\
 	gdk.vcxproj.filters	\
 	gtk.vcxproj	\
 	gtk.vcxproj.filters	\
+	gtk-encode-symbolic-svg.vcxproj	\
+	gtk-encode-symbolic-svg.vcxproj.filters	\
 	gtk3-demo.vcxproj	\
 	gtk3-demo.vcxproj.filters	\
 	gtk3-demo-application.vcxproj	\