Configurable Penalty Costs for Levenshtein

Hi,

Following patch implements configurable penalty costs for levenshtein
distance metric in fuzzystrmatch contrib module.

It doesn't introduce any compatibility issues. Just implements

levenshtein(text,text,int,int,int)

function on top of fuzzystrmatch.c:levenshtein_internal(). At the
same time, levenshtein(text,text) becomes just a wrapper for
levenshtein(text,text,1,1,1) call.

BTW, in current CVS tip

if (cols/rows == 0) ...

checks in fuzzyztrmatch.c:levenshtein() never fail because of

cols/rows = strlen(...) + 1;

FYI.

Regards.