[devel] Bump to version libpng-1.5.1beta06

CHANGES

diff --git a/CHANGES b/CHANGES
index 819d142..6af131f 100644
--- a/CHANGES
+++ b/CHANGES
@@ -3175,6 +3175,8 @@
     char_index, divisor, exp_b10, and gamma_val, respectively, and
     changed exp() back to png_exp().
 
+Version 1.5.1beta06 [January 16, 2011]
+
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