Determines if the string Found is a plausible misspelling of the string Expect. Returns True for an exact match or a probably misspelling, False if no near match is detected. This routine is case sensitive, so the caller should fold both strings to get a case insensitive match.

Note: the spec of this routine is deliberately rather vague. This routine is the one used by GNAT itself to detect misspelled keywords and identifiers, and is heuristically adjusted to be appropriate to this usage. It will work well in any similar case of named entities with relatively short mnemonic names.