ext/annodex/gstcmmlenc.c: Use copies of header buffers for caps to avoid circular refcounting problems (as in theorad...

Original commit message from CVS:
* ext/annodex/gstcmmlenc.c: (gst_cmml_enc_set_header_on_caps):
Use copies of header buffers for caps to avoid circular refcounting
problems (as in theoradec, vorbisdec).

* tests/check/elements/cmmldec.c: (GST_START_TEST):
Fix a typo in test that meant it was testing the wrong thing.

* tests/check/elements/cmmlenc.c: (check_headers):
Fix refcount checks now that we use buffer-copies for caps.