Fix Par[Array].find recomputing callee twice

Currently 

        optimize{optimize{(1 to 10).toArray.find(_>0)}}

expands to 

        val idx = (1 to 10).toArray.findIDX(_ > 0)
        if (idx >= 0) Some((1 to 10).toArray(idx))
        else None

Note target array being recomputed twice.
Same applies to par._
Here's fix :-)
fix for https://github.com/scala-blitz/scala-blitz/issues/26