[libpng15] Bump version to libpng-1.5.6beta04

CHANGES

diff --git a/CHANGES b/CHANGES
index 0426b59..fa7c730 100644
--- a/CHANGES
+++ b/CHANGES
@@ -3613,7 +3613,8 @@
   Revised CMakeLists.txt to work with mingw and removed some material from
     CMakeLists.txt that is no longer useful in libpng-1.5.
 
-Version 1.5.6beta04 [September 28, 2011]
+Version 1.5.6beta04 [October 5, 2011]
+  Fixed typo in Makefile.in and Makefile.am ("-M Wl" should be "-M -Wl")."
 
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