Support 'twisted' RDW headers

[yruslan]

Background

When, say, a record length is 10, RDWs will look like this:
Big-endian: 00 0A 00 00
Little-endian: 00 00 0A 00

But sometimes we encounter:
Big-endian: 00 00 00 0A
Little-endian: 0A 00 00 00

Feature

Add support for these 'twisted' headers by

• Checking if the first 2 bytes of an RDW header is 0, use the second 2 bytes.
• Apply endiness logic to the 2 non-zero bytes.