fix a bug of CvSeq#push
fix a bug of CvSeq#push

CvSeq<Fixnum>#push stores always 0 to sequences in some environments.

  seq = CvSeq.new(Fixnum)
  seq.push(10, 20, 30)
  seq.to_a #=> [10, 20, 30] expected, but [0, 0, 0] returned

This commit fixes the problem.

bonanza-market/ruby-opencv,bonanza-market/ruby-opencv,bonanza-market/ruby-opencv