Use UTF-8 for non-ASCII characters in ChangeLog.

ChangeLog

@@ -7,7 +7,7 @@ Changes in 1.2.8.1 (xx May 2013)
 Changes in 1.2.8 (28 Apr 2013)
 - Update contrib/minizip/iowin32.c for Windows RT [Vollant]
 - Do not force Z_CONST for C++
-- Clean up contrib/vstudio [Ro§]
+- Clean up contrib/vstudio [Roß]
 - Correct spelling error in zlib.h
 - Fix mixed line endings in contrib/vstudio
 
@@ -567,7 +567,7 @@ Changes in 1.2.3.1 (16 August 2006)
 - Update make_vms.com [Zinser]
 - Use -fPIC for shared build in configure [Teredesai, Nicholson]
 - Use only major version number for libz.so on IRIX and OSF1 [Reinholdtsen]
-- Use fdopen() (not _fdopen()) for Interix in zutil.h [BŠck]
+- Use fdopen() (not _fdopen()) for Interix in zutil.h [Bäck]
 - Add some FAQ entries about the contrib directory
 - Update the MVS question in the FAQ
 - Avoid extraneous reads after EOF in gzio.c [Brown]
@@ -1181,7 +1181,7 @@ Changes in 1.0.6 (19 Jan 1998)
         386 asm code replacing longest_match().
    contrib/iostream/ by Kevin Ruland <kevin@rodin.wustl.edu>
         A C++ I/O streams interface to the zlib gz* functions
-   contrib/iostream2/  by Tyge Løvset <Tyge.Lovset@cmr.no>
+   contrib/iostream2/  by Tyge Løvset <Tyge.Lovset@cmr.no>
         Another C++ I/O streams interface
    contrib/untgz/  by "Pedro A. Aranda Guti\irrez" <paag@tid.es>
         A very simple tar.gz file extractor using zlib