Change the type descriptor hash and equal functions from C code pointers
    to Go func values.  This permits them to be set to a Go function
    closure.  This is in preparation for the Go 1.5, so that we can use a
    closure for the hash/equal functions returned by the new reflect.ArrayOf
    function.
    
    Reviewed-on: https://go-review.googlesource.com/16485

From-SVN: r229541