The problem is that the PHP standard function "gzopen" is renamed as "gzopen64".
It may be just a bug at build system.
I think it is caused by macro "#define gzopen gzopen64" in /usr/include/zlib.h (zlib1g-dev :1.2.3.3.dfsg-13ubuntu3).
The unapplyed patch "019-z_off_t_as_long.patch" generates old version zlib.h into ext/zlib.
If the patch is applyed, PHP "gzopen" function is defined beacuse it does not contain the gzopen macro.
The problem is that the PHP standard function "gzopen" is renamed as "gzopen64".
It may be just a bug at build system.
I think it is caused by macro "#define gzopen gzopen64" in /usr/include/zlib.h (zlib1g-dev :1.2.3. 3.dfsg- 13ubuntu3) .
The unapplyed patch "019-z_ off_t_as_ long.patch" generates old version zlib.h into ext/zlib.
If the patch is applyed, PHP "gzopen" function is defined beacuse it does not contain the gzopen macro.