ParseNotificationLevel

Always report the parse problem at this location, unless there are too many places in the parse sequence past this, at which non-silent problems have been recorded.

Only report the parse problem if there is no STRONG theory about what went wrong at the current location.

Only report the parse problem if there is no MEDIUM or STRONG theory about what went wrong at the current location.

Never report the parse problem, and don't include the current error location as a potential place at which to describe expectations (potential syntax errors) unless there is a stronger (i.e., non-{code SILENT}) problem at the same position.