As you may know, many things changed in OpenCV 3 (in comparision to the openCV2 or the old first version).
In the old days, to train SVM one would use:
I know this is an old post, but i came across it looking for the same solution. This tutorial is extremely helpful: http://docs.opencv.org/3.0-beta/doc/tutorials/ml/introduction_to_svm/introduction_to_svm.html