[devel] Swapped PNG_UNKNOWN_CHUNKS_SUPPORTED and PNG_HANDLE_AS_UNKNOWN_SUPPORTED

in pngset.c to be consistent with other changes in version 1.2.38.
diff --git a/pngset.c b/pngset.c
index 737bf36..b9981f0 100644
--- a/pngset.c
+++ b/pngset.c
@@ -1,7 +1,7 @@
 
 /* pngset.c - storage of image information into info struct
  *
- * Last changed in libpng 1.4.0 [December 22, 2009]
+ * Last changed in libpng 1.4.0 [December 25, 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.)
@@ -932,7 +932,7 @@
 }
 #endif /* PNG_sPLT_SUPPORTED */
 
-#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
+#ifdef PNG_UNKNOWN_CHUNKS_SUPPORTED
 void PNGAPI
 png_set_unknown_chunks(png_structp png_ptr,
    png_infop info_ptr, png_unknown_chunkp unknowns, int num_unknowns)
@@ -1016,7 +1016,7 @@
 }
 #endif
 
-#ifdef PNG_UNKNOWN_CHUNKS_SUPPORTED
+#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
 void PNGAPI
 png_set_keep_unknown_chunks(png_structp png_ptr, int keep, png_bytep
    chunk_list, int num_chunks)