[vala-extra-vapis] opencv: Use CCode free_function instead of unavailable has_free_function

[Rico Tzschichholz <ricotz src gnome org>]

commit 4b50fa697348f2c7f4167bd570e6bcfe4bfdbdcf
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Wed Jan 30 21:22:32 2019 +0100

    opencv: Use CCode free_function instead of unavailable has_free_function

 opencv.vapi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/opencv.vapi b/opencv.vapi
index 36a3f1f..93205b5 100644
--- a/opencv.vapi
+++ b/opencv.vapi
@@ -427,7 +427,7 @@ namespace OpenCV {
                public int line_type;
        }
 
-       [Compact, CCode (cname = "CvHaarClassifierCascade", has_free_function = false)]
+       [Compact, CCode (cname = "CvHaarClassifierCascade", free_function = "")]
        public class HaarClassifierCascade {
                [CCode (cname = "cvLoad", type = "void*")]
                public static unowned HaarClassifierCascade? load (string filename, OpenCV.Memory.Storage 
storage, string? name = null, out string? real_name = null);