facedetect: handle haardetect max-size settings in plugin properties
Submitted by flavie lancereau
Since version 2.2 of opencv, a parameter appeared in the haardetect function, this is the maximum size. This one allows to limit the number of iteration of the search and thus to optimize this one. By default in gstreamer this parameter is set to CvSize(0,0) so no limitation, however it would be useful to be able to modify it in the plugin properties.