Restore png_combine_row() to progressive-read-only builds.

ANNOUNCE

@@ -455,8 +455,8 @@ version 1.4.0beta59 [May 15, 2009]
   Relocated misplaced #endif in pngwrite.c, sCAL chunk handler.
 
 version 1.4.0beta60 [May 18, 2009]
-  Conditionally compile png_combine_row() and png_read_finish_row()
-    which are not used by progressive readers.
+  Conditionally compile png_read_finish_row() which is not used by
+    progressive readers.
 
 version 1.4.0betaN [future]
   Build shared libraries with -lz and sometimes -lm.

CHANGES

@@ -2132,8 +2132,8 @@ version 1.4.0beta59 [May 15, 2009]
   Relocated misplaced #endif in pngwrite.c, sCAL chunk handler.
 
 version 1.4.0beta60 [May 18, 2009]
-  Conditionally compile png_combine_row() and png_read_finish_row()
-    which are not used by progressive readers.
+  Conditionally compile png_read_finish_row() which is not used by
+    progressive readers.
 
 version 1.4.0betaN [future]
   Build shared libraries with -lz and sometimes -lm.

pngrutil.c

@@ -2404,7 +2404,6 @@ png_check_chunk_name(png_structp png_ptr, png_bytep chunk_name)
    }
 }
 
-#ifndef PNG_NO_SEQUENTIAL_READ_SUPPORTED
 /* Combines the row recently read in with the existing pixels in the
    row.  This routine takes care of alpha and transparency if requested.
    This routine also handles the two methods of progressive display
@@ -2616,7 +2615,6 @@ png_combine_row(png_structp png_ptr, png_bytep row, int mask)
       }
    }
 }
-#endif /* PNG_NO_SEQUENTIAL_READ_SUPPORTED */
 
 #ifdef PNG_READ_INTERLACING_SUPPORTED
 /* OLD pre-1.0.9 interface: