Function syntax::util::lev_distance::find_best_match_for_name

pub fn find_best_match_for_name<'a, T>(
    iter_names: T, 
    lookup: &str, 
    dist: Option<usize>
) -> Option<Symbol> where
    T: Iterator<Item = &'a Symbol>, 

Finds the best match for a given word in the given iterator

As a loose rule to avoid the obviously incorrect suggestions, it takes an optional limit for the maximum allowable edit distance, which defaults to one-third of the given word.

Besides Levenshtein, we use case insensitive comparison to improve accuracy on an edge case with a lower(upper)case letters mismatch.