[libpng16] Removed #ifdef PNG_16BIT_SUPPORTED/#endif around png_product2(); it is

    needed by png_reciprocal2().
Added #ifdef PNG_16BIT_SUPPORTED/#endif around png_log16bit() and
    png_do_swap().
diff --git a/pngrtran.c b/pngrtran.c
index 8d7904c..d7a4f1b 100644
--- a/pngrtran.c
+++ b/pngrtran.c
@@ -4962,7 +4962,7 @@
 
 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
    if ((png_ptr->transformations & PNG_USER_TRANSFORM) != 0)
-    {
+   {
       if (png_ptr->read_user_transform_fn != NULL)
          (*(png_ptr->read_user_transform_fn)) /* User read transform function */
              (png_ptr,     /* png_ptr */