New pjmedia_codec_register_all() API and deregister automatically on shutdown

[bennylp]

New API to register all known codecs, and to automatically deregister them on shutdown:

/* file <pjmedia-codec/audio_codecs.h> */

/**
 * Codec configuration. Call #pjmedia_audio_codec_config_default() to initialize
 * this structure with the default values.
 */
typedef struct pjmedia_audio_codec_config
{
    /** Speex codec settings. See #pjmedia_codec_speex_init() for more info */
    struct {
	unsigned	option;		/**< Bitmask of options.	*/
	unsigned	quality;	/**< Codec quality.		*/
	unsigned	complexity;	/**< Codec complexity.		*/
    } speex;

    /** iLBC settings */
    struct {
	unsigned	mode;		/**< iLBC mode.			*/
    } ilbc;

    /** Passthrough */
    struct {
	pjmedia_codec_passthrough_setting setting; /**< Passthrough	*/
    } passthrough;

} pjmedia_audio_codec_config;


/**
 * Initialize pjmedia_audio_codec_config structure with default values.
 *
 * @param cfg		The codec config to be initialized.
 */
PJ_DECL(void) pjmedia_audio_codec_config_default(pjmedia_audio_codec_config *cfg);

/**
 * Register all known audio codecs implemented in PJMEDA-CODEC library to the
 * specified media endpoint.
 *
 * @param endpt		The media endpoint.
 * @param c		Optional codec configuration, or NULL to use default
 * 			values.
 *
 * @return		PJ_SUCCESS on success or the appropriate error code.
 */
PJ_DECL(pj_status_t)
pjmedia_codec_register_audio_codecs(pjmedia_endpt *endpt,
                                    const pjmedia_audio_codec_config *c);

Note to codec writers:

A new mandatory destroy callback has been added to factory operation. You must implement this callback (hint: just point it to your existing function that deinitialize your codec factory).

Note to app writers:

You don't need to initialize each codec now, just use pjmedia_codec_register_audio_codecs() above. Similarly you should remove all the calls to codec deinitialization routines since that will be done automatically when the media endpoint is destroyed (leaving these calls as they are is harmless though; they will render to no-ops).