Expanded and rewrote large parts of this submission. I thought it would be more straightforward to break down a practical example and show readers exactly how a string of bits would be interpreted by another node.
I corrected an error from yesterday because I mistakenly did not realize that despite bit 2 not being used, bits 2 and 3 still form a "pair", so my count was off. One part I'm not 100% sure of is if I've read the string correctly. From right to left, I read bits 8 and 9 as "01", which is enabled and odd, so 'var_onion_optin' is enabled and backwards-compatible. Is this correct?
