This calculates the similarity between two strings as described in Oliver
[1993]. Note that this implementation does not use a stack as in Oliver's
pseudo code, but recursive calls which may or may not speed up the whole
process. Note also that the complexity of this algorithm is O(N**3) where
N is the length of the longest string.
Parameters
first
The first string.
second
The second string.
percent
By passing a reference as third argument,
similar_text() will calculate the similarity in
percent for you.
Return Values
Returns the number of matching chars in both strings.