Revert "png_reset_prev_row" from png.h and pngrutil.c

This should be handled in the APNG fork, not in libpng proper.

png.h

 /* png.h - header file for PNG reference library
  *
- * libpng version 1.2.37beta02 - May 15, 2009
+ * libpng version 1.2.37beta02 - May 18, 2009
  * Copyright (c) 1998-2009 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -8,7 +8,7 @@
  * Authors and maintainers:
  *  libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
  *  libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger
- *  libpng versions 0.97, January 1998, through 1.2.37beta02 - May 15, 2009: Glenn
+ *  libpng versions 0.97, January 1998, through 1.2.37beta02 - May 18, 2009: Glenn
  *  See also "Contributing Authors", below.
  *
  * Note about libpng version numbers:
@@ -256,7 +256,7 @@
  * If you modify libpng you may insert additional notices immediately following
  * this sentence.
  *
- * libpng versions 1.2.6, August 15, 2004, through 1.2.37beta02, May 15, 2009, are
+ * libpng versions 1.2.6, August 15, 2004, through 1.2.37beta02, May 18, 2009, are
  * Copyright (c) 2004, 2006-2009 Glenn Randers-Pehrson, and are
  * distributed according to the same disclaimer and license as libpng-1.2.5
  * with the following individual added to the list of Contributing Authors:
@@ -368,7 +368,7 @@
  * Y2K compliance in libpng:
  * =========================
  *
- *    May 15, 2009
+ *    May 18, 2009
  *
  *    Since the PNG Development group is an ad-hoc body, we can't make
  *    an official declaration.
@@ -432,7 +432,7 @@
 /* Version information for png.h - this should match the version in png.c */
 #define PNG_LIBPNG_VER_STRING "1.2.37beta02"
 #define PNG_HEADER_VERSION_STRING \
-   " libpng version 1.2.37beta02 - May 15, 2009\n"
+   " libpng version 1.2.37beta02 - May 18, 2009\n"
 
 #define PNG_LIBPNG_VER_SONUM   0
 #define PNG_LIBPNG_VER_DLLNUM  13

pngrutil.c

@@ -2920,6 +2920,8 @@ png_read_finish_row(png_structp png_ptr)
    if (png_ptr->interlaced)
    {
       png_ptr->row_number = 0;
+      png_memset_check(png_ptr, png_ptr->prev_row, 0,
+         png_ptr->rowbytes + 1);
       do
       {
          png_ptr->pass++;
@@ -3211,15 +3213,7 @@ defined(PNG_USER_TRANSFORM_PTR_SUPPORTED)
       png_memset_check(png_ptr, png_ptr->prev_row, 0, row_bytes + 1);
       png_ptr->old_prev_row_size = row_bytes + 1;
    }
-   else
-   {
-      if (png_ptr->reset_prev_row == 1)
-      {
-         png_memset_check(png_ptr, png_ptr->prev_row, 0, row_bytes + 1);
-      }
-   }
 
-   png_ptr->reset_prev_row = 0;  
    png_ptr->rowbytes = row_bytes;
 
    png_debug1(3, "width = %lu,", png_ptr->width);