add back pngwrite read on all configs

Author: weareu

Diff for: binding.gyp

@@ -50,6 +50,7 @@
             "src/lib/png/pngrutil.c",
             "src/lib/png/pngtrans.c",
             "src/lib/png/pngread.c",
+            "src/lib/png/pngwrite.c",
             "src/lib/png/pngrio.c",
             "src/lib/png/pngrtran.c",
             "src/lib/png/pngmem.c",
@@ -166,6 +167,7 @@
             "src/lib/png/pngtrans.c",
             "src/lib/png/pngmem.c",
             "src/lib/png/pngerror.c",
+            "src/lib/png/pngread.c",
             "src/lib/png/pngwrite.c",
             "src/lib/png/pngwutil.c",
             "src/lib/png/pngwio.c",
@@ -290,4 +292,4 @@
             }]
         ]
     }]
-}
+}