Png: compatibility with libpng 1.4

Patch probably from arekm -- pld-linux . org

modules/codec/png.c

@@ -152,7 +152,7 @@ static picture_t *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
     p_info = png_create_info_struct( p_png );
     if( p_info == NULL )
     {
-        png_destroy_read_struct( &p_png, png_infopp_NULL, png_infopp_NULL );
+        png_destroy_read_struct( &p_png, NULL, NULL );
         block_Release( p_block ); *pp_block = NULL;
         return NULL;
     }
@@ -160,7 +160,7 @@ static picture_t *DecodeBlock( decoder_t *p_dec, block_t **pp_block )
     p_end_info = png_create_info_struct( p_png );
     if( p_end_info == NULL )
     {
-        png_destroy_read_struct( &p_png, &p_info, png_infopp_NULL );
+        png_destroy_read_struct( &p_png, &p_info, NULL );
         block_Release( p_block ); *pp_block = NULL;
         return NULL;
     }