Check libpng directly into third_party/

third_party/libpng/projects/visualc71/README_zlib.txt

+/* WARNING: This file was put in the LibPNG distribution for convenience only.
+            It is expected to be part of the next zlib release under
+            "projects\visualc71\README.txt." */
+
+Microsoft Developer Studio Project File, Format Version 7.10 for zlib.
+
+Copyright (C) 2004 Simon-Pierre Cadieux.
+Copyright (C) 2004 Cosmin Truta.
+
+This code is released under the libpng license.
+For conditions of distribution and use, see copyright notice in zlib.h.
+
+NOTE: This project will be removed from libpng-1.5.0.  It has
+been replaced with the "vstudio" project.
+
+To use:
+
+1) On the main menu, select "File | Open Solution".
+   Open "zlib.sln".
+
+2) Display the Solution Explorer view (Ctrl+Alt+L)
+
+3) Set one of the project as the StartUp project. If you just want to build the
+   binaries set "zlib" as the startup project (Select "zlib" tree view item +
+   Project | Set as StartUp project). If you want to build and test the
+   binaries set it to "example" (Select "example" tree view item + Project |
+   Set as StartUp project), If you want to build the minigzip utility set it to
+   "minigzip" (Select "minigzip" tree view item + Project | Set as StartUp
+   project
+
+4) Select "Build | Configuration Manager...".
+   Choose the configuration you wish to build.
+
+5) Select "Build | Clean Solution".
+
+6) Select "Build | Build Solution (Ctrl-Shift-B)"
+
+This project builds the zlib binaries as follows:
+
+* Win32_DLL_Release\zlib1.dll       DLL build
+* Win32_DLL_Debug\zlib1d.dll        DLL build (debug version)
+* Win32_LIB_Release\zlib.lib        static build
+* Win32_LIB_Debug\zlibd.lib         static build (debug version)
+