elm - fix selection debug print to not print unterminated buffers

so it's printfing a non-0 byte terminated string ... it's a
buffer/slice which has explicit lenmgth and no nul, so fwrite it
approplriately.

src/lib/elementary/efl_selection.c

@@ -172,7 +172,10 @@ struct _Cnp_Data_Cb_Wrapper
 static void
 _selection_data_ready_cb(void *data, Efl_Object *obj, Efl_Selection_Data *seldata)
 {
-    printf("obj: %p, data: %s, length: %zd\n", obj, (char *)seldata->content.mem, seldata->content.len);
+   printf("obj: %p, data: [", obj);
+   fwrite(seldata->content.mem, seldata->content.len, 1, stdout);
+   printf("], length: %zd\n", seldata->content.len);
+
     Cnp_Data_Cb_Wrapper *wdata = data;
     if (!wdata) return;
     Elm_Selection_Data ddata;