Fix little error on Jaro Similarity

This error cause break during execution time, and comparing this
situation with version in .NET:
.Net: Math.Min(i + distanceSep, secondWord.Length);

C: int min = MIN(i + d_step, ((int)strlen(str2) - 1));  (error !)
C: int min = MIN(i + d_step, (int)strlen(str2) ); (correct !)

Thank!