devel/zziplib: fix build with clang 15

During an exp-run for llvm 15 (see bug 265425), it turned out that
devel/zziplib failed to build with clang (and lld) 15:

/wrkdirs/usr/ports/devel/zziplib/work/zziplib-0.13.72/zzip/mmapped.c:664:11: error: incompatible pointer to integer conversion initializing 'off_t' (aka 'long') with an expression of type 'zzip_byte_t *' (aka 'unsigned char *') [-Wint-conversion]

off_t offset = zzip_file_header_to_data(header);
      ^        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

/wrkdirs/usr/ports/devel/zziplib/work/zziplib-0.13.72/zzip/mmapped.c:666:34: warning: incompatible pointer types initializing 'struct zzip_extra_zip64 *' with an expression of type 'char *' [-Wincompatible-pointer-types]

struct zzip_extra_zip64* zip64 =
                         ^

/wrkdirs/usr/ports/devel/zziplib/work/zziplib-0.13.72/zzip/mmapped.c:673:34: warning: incompatible pointer types initializing 'struct zzip_extra_zip64 *' with an expression of type 'char *' [-Wincompatible-pointer-types]

struct zzip_extra_zip64* zip64 =
                         ^

/wrkdirs/usr/ports/devel/zziplib/work/zziplib-0.13.72/zzip/mmapped.c:685:24: error: incompatible integer to pointer conversion assigning to 'Bytef *' (aka 'unsigned char *') from 'off_t' (aka 'long') [-Wint-conversion]

file->zlib.next_in = offset;
                   ^ ~~~~~~

2 warnings and 2 errors generated.

Use the patch from https://github.com/gdraheim/zziplib/issues/140 to fix
the errors.

PR: 268185
Approved by: portmgr (tcberner)
MFH: 2022Q4