unusual type conversion in invoke

[Per Bothner]

I did a little bit of playing around with this.
I agree preferring indexoF(String) over indexOf(int)
ia wrong, but it doesn't look like a simple fix,
and I think it is best to defer dealing with the
issue until after Kawa 1.7 is released.

Note there is already some special-case code for the
"tostring_type" i.e. java.lang.String case, mostly
to give that case lower-priority, but it doesn't
solve this particular problem.  I suspect we may want
three levels of type conversion:
   1. widening conversions (e.g. String->Object, int->double)
   2. narrowing conversions (e.g. Object->Number)
   3. special conversions (Object->String, perhaps list->array)
-- 
	--Per Bothner
per@bothner.com   http://per.bothner.com/