I attached patch for latest code.

As required, now by default we compare the string by character. So
it can handle multibyte character correctly. 

'string-distance' has third optional parameter 'bytecompare' which
use byte comparing instead of default character comparing.

I did read this thread carefully and I did know different algorithms
exist to calculate string distance.

But I feel only my code is the right solution to our original problem.

Our original problem is to provide a faster C solution to calculate
*Levenshtein distance*.

It will replace 3rd party Lisp solution like 'org-babel-edit-distance'.

As 'org-babel-edit-distance' documented, it will "Return the edit
(levenshtein) distance between strings S1 S2". So the problem here is to
calculate *Levenshtein distance*.

Other algorithms have their own definition of "string distance" so they
are not for *Levenshtein distance*.

Here is link of "Comparison of String Distance Algorithms":

https://www.joyofdata.de/blog/comparison-of-string-distance-algorithms/