many1Till quirk can cause stack overflows and O(n!) parser complexity with recursive grammars

[zotanmew]

Unlike manyTill p endp, many1Till p endp runs p first, even if endp would match immediately. This, when used in a recursive grammar, can cause parsers that work perfectly fine on most inputs to produce stack overflows - despite a modest recursion depth of <10, and can cause inputs of reasonable length to stall for long / indefinite periods (I think O(n!)).

The documentation currently reads:

The parser many1Till p endp behaves like manyTill p endp, except that it requires p to succeed at least one time.

many1Till p endp is an optimized implementation of pipe2 p (manyTill p endp) (fun hd tl -> hd::tl)

I would suggest that many1Till (and skipMany1Till) be changed to the equivalent of notFollowedBy endp >>. many1Till p endp. If that behavior change is not wanted, I'd strongly recommend documenting this quirk in a more obvious way, and with a disclaimer that this can cause problems with recursive grammars.

I'm also not sure if similar issues exist in other primitives - this is the only one I've encountered so far.