[libpng16] Bump version to 1.6.26beta04

ANNOUNCE

@@ -1,4 +1,4 @@
-Libpng 1.6.26beta03 - October 2, 2016
+Libpng 1.6.26beta04 - October 3, 2016
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -8,20 +8,20 @@ Files available for download:
 Source files with LF line endings (for Unix/Linux) and with a
 "configure" script
 
-   1.6.26beta03.tar.xz (LZMA-compressed, recommended)
-   1.6.26beta03.tar.gz
+   1.6.26beta04.tar.xz (LZMA-compressed, recommended)
+   1.6.26beta04.tar.gz
 
 Source files with CRLF line endings (for Windows), without the
 "configure" script
 
-   lp1626b03.7z  (LZMA-compressed, recommended)
-   lp1626b03.zip
+   lp1626b04.7z  (LZMA-compressed, recommended)
+   lp1626b04.zip
 
 Other information:
 
-   1.6.26beta03-README.txt
-   1.6.26beta03-LICENSE.txt
-   libpng-1.6.26beta03-*.asc (armored detached GPG signatures)
+   1.6.26beta04-README.txt
+   1.6.26beta04-LICENSE.txt
+   libpng-1.6.26beta04-*.asc (armored detached GPG signatures)
 
 Changes since the last public release (1.6.25):
 
@@ -49,13 +49,15 @@ Version 1.6.26beta02 [October 1, 2016]
     flag definitions in pngpriv.h from 0xnnnn to 0xnnnnU and trivial changes
     in png.c, pngread.c, and pngwutil.c.
 
-Version 1.6.26beta03 [October 2, 2016]
+Version 1.6.26beta03 [October 3, 2016]
   Removed contrib/libtests/*.orig and *.rej that slipped into the tarballs.
   Quieted the 86 remaining -Wconversion compiler warnings by
     revising the png_isaligned() macro and trivial changes in png.c,
     pngerror.c, pngget.c, pngmem.c, pngset.c, pngrtran.c, pngrutil.c,
     pngwtran.c, pngwrite.c, and pngwutil.c.
 
+Version 1.6.26beta04 [October 3, 2016]
+
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