Improper condition was introduced in 1.2.5 causing some applications
(e.g. cgit) to fail due to conflicting declarations.

References:
- http://mail.madler.net/pipermail/zlib-devel_madler.net/2010-May/002249.html
- http://bugs.debian.org/439980
- http://bugs.gentoo.org/show_bug.cgi?id=316377
- http://bugs.gentoo.org/show_bug.cgi?id=316855
- http://bugs.archlinux.org/task/19280
- https://bugs.launchpad.net/ubuntu/+source/libpciaccess/+bug/402178

--- zlib-1.2.5/zlib.h.orig	2010-04-20 06:12:48.000000000 +0200
+++ zlib-1.2.5/zlib.h	2010-05-24 21:28:52.465538337 +0200
@@ -1562,7 +1562,7 @@
  * functions are changed to 64 bits) -- in case these are set on systems
  * without large file support, _LFS64_LARGEFILE must also be true
  */
-#if defined(_LARGEFILE64_SOURCE) && _LFS64_LARGEFILE-0
+#if (defined(_LARGEFILE64_SOURCE) || (_FILE_OFFSET_BITS-0 == 64)) && _LFS64_LARGEFILE-0
    ZEXTERN gzFile ZEXPORT gzopen64 OF((const char *, const char *));
    ZEXTERN z_off64_t ZEXPORT gzseek64 OF((gzFile, z_off64_t, int));
    ZEXTERN z_off64_t ZEXPORT gztell64 OF((gzFile));
@@ -1578,14 +1578,6 @@
 #  define gzoffset gzoffset64
 #  define adler32_combine adler32_combine64
 #  define crc32_combine crc32_combine64
-#  ifdef _LARGEFILE64_SOURCE
-     ZEXTERN gzFile ZEXPORT gzopen64 OF((const char *, const char *));
-     ZEXTERN z_off_t ZEXPORT gzseek64 OF((gzFile, z_off_t, int));
-     ZEXTERN z_off_t ZEXPORT gztell64 OF((gzFile));
-     ZEXTERN z_off_t ZEXPORT gzoffset64 OF((gzFile));
-     ZEXTERN uLong ZEXPORT adler32_combine64 OF((uLong, uLong, z_off_t));
-     ZEXTERN uLong ZEXPORT crc32_combine64 OF((uLong, uLong, z_off_t));
-#  endif
 #else
    ZEXTERN gzFile ZEXPORT gzopen OF((const char *, const char *));
    ZEXTERN z_off_t ZEXPORT gzseek OF((gzFile, z_off_t, int));