faceblur: set maximum feature size to 0x0

Previously faces would only be detected if they were at least 30x30 pixels
large and at most 32x32 pixels. We keep the minimum setting (maybe needs
a property as in facedetect) but disable the maximum feature size.

See https://bugzilla.gnome.org/show_bug.cgi?id=722158

ext/opencv/gstfaceblur.c

@@ -280,7 +280,7 @@ gst_face_blur_chain (GstPad * pad, GstObject * parent, GstBuffer * buf)
         cvHaarDetectObjects (filter->cvGray, filter->cvCascade,
         filter->cvStorage, 1.1, 2, 0, cvSize (30, 30)
 #if (CV_MAJOR_VERSION >= 2) && (CV_MINOR_VERSION >= 2)
-        , cvSize (32, 32)
+        , cvSize (0, 0)
 #endif
         );