Use network byte order for wzip and wunzip test files

[xxyzz]

Now no matter which byte order the system uses, if we use htonl and ntohl correctly, we will pass all the tests.

// before
$ xxd -b -c 5 tests/4.in
00000000: 00111010 00000000 00000000 00000000 01100001  :...a
00000005: 00000001 00000000 00000000 00000000 00001010  .....
0000000a: 00011111 00000000 00000000 00000000 01100010  ....b
0000000f: 00000001 00000000 00000000 00000000 00001010  .....
00000014: 00010100 00000000 00000000 00000000 01100011  ....c
00000019: 00000001 00000000 00000000 00000000 00001010  .....
0000001e: 00011111 00000000 00000000 00000000 01100100  ....d
00000023: 00000001 00000000 00000000 00000000 00001010  .....
00000028: 01111001 00000001 00000000 00000000 01100101  y...e
0000002d: 00000001 00000000 00000000 00000000 00001010  .....

// after
$ xxd -b -c 5 tests/4.in
00000000: 00000000 00000000 00000000 00111010 01100001  ...:a
00000005: 00000000 00000000 00000000 00000001 00001010  .....
0000000a: 00000000 00000000 00000000 00011111 01100010  ....b
0000000f: 00000000 00000000 00000000 00000001 00001010  .....
00000014: 00000000 00000000 00000000 00010100 01100011  ....c
00000019: 00000000 00000000 00000000 00000001 00001010  .....
0000001e: 00000000 00000000 00000000 00011111 01100100  ....d
00000023: 00000000 00000000 00000000 00000001 00001010  .....
00000028: 00000000 00000000 00000001 01111001 01100101  ...ye
0000002d: 00000000 00000000 00000000 00000001 00001010  .....

[xxyzz]

Hi @remzi-arpacidusseau, would you please review this pull request if you have time?