[ocaml/en] Syntax error fix and minor enhancements

Fixed a syntax error in pattern matching section that would lead to unexpected results.
Removed horizontal scrolling. Clarified some stuff.
Commented on wrong thing, sorry. On this issue: no, it's a poor substitute for a lower index that is supposed to indicate that it's a new function based on the original one. I know this explanation is not very readable, but I think the signature format does need some explanation. If you think otherwise, I can remove the explanation attempt.