Check libpng directly into third_party/

third_party/libpng/projects/visualc71/README.txt

+Microsoft Developer Studio Project File, Format Version 7.10 for libpng.
+
+Copyright (C) 2004 Simon-Pierre Cadieux.
+
+This code is released under the libpng license.
+For conditions of distribution and use, see copyright notice in png.h
+
+NOTE: This project will be removed from libpng-1.5.0.  It has
+been replaced with the "vstudio" project.
+
+Assumptions:
+* The libpng source files are in ..\..
+* The zlib source files are in ..\..\..\zlib
+* The zlib project file is in . /* Warning: This is until the zlib project
+  files get intergrated into the next zlib release. The final zlib project
+  directory will then be ..\..\..\zlib\projects\visualc71. */
+
+To use:
+
+1) On the main menu, select "File | Open Solution".
+   Open "libpng.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 "libpng" as the startup project (Select "libpng" tree view
+   item + Project | Set as StartUp project). If you want to build and test the
+   binaries set it to "pngtest" (Select "pngtest" 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 libpng binaries as follows:
+
+* Win32_DLL_Release\libpng16.dll      DLL build
+* Win32_DLL_Debug\libpng16d.dll       DLL build (debug version)
+* Win32_DLL_VB\libpng16vb.dll         DLL build for Visual Basic, using stdcall
+* Win32_LIB_Release\libpng.lib        static build
+* Win32_LIB_Debug\libpngd.lib         static build (debug version)
+
+Notes:
+
+If you change anything in the source files, or select different compiler
+settings, please change the DLL name to something different than any of
+the above names. Also, make sure that in your "pngusr.h" you define
+PNG_USER_PRIVATEBUILD and PNG_USER_DLLFNAME_POSTFIX according to the
+instructions provided in "pngconf.h".
+
+All DLLs built by this project use the Microsoft dynamic C runtime library
+MSVCR71.DLL (MSVCR71D.DLL for debug versions).  If you distribute any of the
+above mentioned libraries you may have to include this DLL in your package.
+For a list of files that are redistributable in Visual Studio see
+$(VCINSTALLDIR)\redist.txt.