parsers: drop spurious check of readlen value
We're about to check if len < 40 after assigning readlen to len, which
means that if len < 40 we'll still abort, but I'm about to add a
sensible exception to that failure, so let's just discard this useless
check.
Ancestors of 5
4 2 0
Ancestors of 6 and 5
3 4 2 1 0
Ancestors of 5 and 4
4 2 0
Ancestors of 7, stop at 6
6
Ancestors of 7, including revs
7 6 5 3 4 2 1 0
Ancestors of 7, 5 and 3, including revs
7 5 3 6 4 2 1 0
Descendants of 5
7 8
Descendants of 5 and 3
6 7 8
Descendants of 5 and 4
5 7 8