Can the rejectReason values in errors.go be exported (i.e. capitalized) so we can use them? #788

It's weird that NewMessageRejectError and the like are exported, but the values intended to be used for the rejectReason int param are private (e.g. rejectReasonInvalidTagNumber, rejectReasonRequiredTagMissing, etc).

If my own code calls NewMessageRejectError(err,rejectReason,refTagID), then rejectReason must be specified with e.g. 5 or my own lookalike constant instead of me being able to use quickfix.RejectReasonValueIsIncorrect.

If preserving the existing interface wasn't a concern, I'd suggest creating a type RejectReason int and switching all the functions to use it, but that would break compatibility.

However, it would not break compatibility to simply change all the rejectReason* int constants to be caplitalized.

If I submitted such a change would it be accepted? Or is there some other complication that would make this not feasable