od: add 4-byte hex dump option

[mknos]

• GNU and OpenBSD support "od -H" and "od -X" options for 4-byte hex format, so add it here too
• Rename 2-byte hex format function to avoid conflict with perl built-in hex()
• Bump program version

[briandfoy]

changes: add -H and -X options for 4-byte hex output