[sm130futures] Good on Windows...and Mac too?

We'll see if I'm lucky here.

src/RageSurface_Load_PNG.cpp

@@ -7,9 +7,9 @@
 
 
 #if defined(_WINDOWS)
-#  include "libpng/include/png.h"
+#  include "../extern/libpng/include/png.h"
 #  if defined(_MSC_VER)
-#  pragma comment(lib, "libpng/lib/libpng.lib")
+#  pragma comment(lib, "../extern/libpng/lib/libpng.lib")
 #  pragma warning(disable: 4611) /* interaction between '_setjmp' and C++ object destruction is non-portable */
 #  endif // _MSC_VER
 #else