check lsmash_create_codec_specific_data() failure

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>
configure: Fix out-of-tree build
box: Add the definition of missing lsmash_form_box_type().
lib: Support Opus-in-ISOBMFF.

Don't distribute generated Opus-in-ISOBMFF files.
It is highly experimental stage at present.