gzseek64
ZEXTERN z_off64_t ZEXPORT gzseek64(gzFile, z_off64_t, int);
ret = gzseek64(file, (z_off64_t)offset, whence);
ZEXTERN z_off64_t ZEXPORT gzseek64(gzFile, z_off64_t, int);
# define gzseek gzseek64
ZEXTERN z_off_t ZEXPORT gzseek64(gzFile, z_off_t, int);