[libpng17] Changed pngvalid.c to support libpng 1.5, which does not support

the PNG_MAXIMUM_INFLATE_WINDOW option, so #define it out when
appropriate in pngvalid.c

contrib/libtests/pngvalid.c

@@ -10339,10 +10339,12 @@ int main(int argc, char **argv)
 
          else
 #endif
+#ifdef PNG_MAXIMUM_INFLATE_WINDOW
          if (strncmp(arg, "max-inflate-window:", 19) == 0)
             option = PNG_MAXIMUM_INFLATE_WINDOW, arg += 19;
 
          else
+#endif
          {
             fprintf(stderr, "pngvalid: %s: %s: unknown option\n", *argv, arg);
             exit(99);