Gst::Buffer: fixed copy method

    * gstreamer/src/buffer.ccg: copy method should take ownership of new
      buffer, and shouldn't increase refcount.
    * gstreamer/src/miniobject.hg: added missing <map> header.
    * tests/test-buffer.cc: added test which checks refcout after copying
      buffer.
Gst::Query: fixed QueryCaps::parse method

    * gstreamer/src/query.ccg: QueryCaps::parse method didn't increase
      caps object reference during wrapping, but it should, because of new
      RefPtr pointer, which is created in this method.