[devel] Added a section in documentation

about using png_set_io_ptr() in configure scripts for detecting libpng
diff --git a/CHANGES b/CHANGES
index 0a0ac50..fa0e564 100644
--- a/CHANGES
+++ b/CHANGES
@@ -2143,10 +2143,12 @@
     accordingly.
   More reformatting of comments, mostly to capitalize sentences.
 
-version 1.4.0beta62 [May 31, 2009]
+version 1.4.0beta62 [June 2, 2009]
   Added "#define PNG_NO_WRITE_SWAP" to contrib/pngminim/encoder/pngusr.h
     and "define PNG_NO_READ_SWAP" to decoder/pngusr.h and preader/pngusr.h
   Reformatted several remaining "else statement" into two lines.
+  Added a section about using png_get_io_ptr() in configure scripts to detect
+    the presence of libpng.
 
 version 1.4.0betaN [future]
   Build shared libraries with -lz and sometimes -lm.