Stasis application WebSocket support

This is the API that binds the Stasis dialplan application to external
Stasis applications. It also adds the beginnings of WebSocket
application support.

This module registers a dialplan function named Stasis, which is used
to put a channel into the named Stasis app. As a channel enters and
leaves the Stasis diaplan application, the Stasis app receives a
'stasis-start' and 'stasis-end' events.

Stasis apps register themselves using the stasis_app_register and
stasis_app_unregister functions. Messages are sent to an application
using stasis_app_send.

Finally, Stasis apps control channels through the use of the
stasis_app_control object, and the family of stasis_app_control_*
functions.

Other changes along for the ride are:
 * An ast_frame_dtor function that's RAII_VAR safe
 * Some common JSON encoders for name/number, timeval, and
   context/extension/priority

Review: https://reviewboard.asterisk.org/r/2361/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@384879 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/json.h

@@ -764,4 +764,48 @@ struct ast_json *ast_json_deep_copy(const struct ast_json *value);
 
 /*!@}*/
 
+/*!@{*/
+
+/*!
+ * \brief Common JSON rendering functions for common 'objects'.
+ */
+
+/*!
+ * \brief Simple name/number pair.
+ * \param name Name
+ * \param number Number
+ * \return NULL if error (non-UTF8 characters, NULL inputs, etc.)
+ * \return JSON object with name and number fields
+ */
+struct ast_json *ast_json_name_number(const char *name, const char *number);
+
+/*!
+ * \brief Construct a timeval as JSON.
+ *
+ * JSON does not define a standard date format (boo), but the de facto standard
+ * is to use ISO 8601 formatted string. We build a millisecond resolution string
+ * from the \c timeval
+ *
+ * \param tv \c timeval to encode.
+ * \param zone Text string of a standard system zoneinfo file.  If NULL, the system localtime will be used.
+ * \return JSON string with ISO 8601 formatted date/time.
+ * \return \c NULL on error.
+ */
+struct ast_json *ast_json_timeval(const struct timeval *tv, const char *zone);
+
+/*!
+ * \brief Construct a context/exten/priority as JSON.
+ *
+ * If a \c NULL is passed for \c context or \c exten, or -1 for \c priority,
+ * the fields is set to ast_json_null().
+ *
+ * \param context Context name.
+ * \param exten Extension.
+ * \param priority Dialplan priority.
+ * \return JSON object with \c context, \c exten and \c priority fields
+ */
+struct ast_json *ast_json_dialplan_cep(const char *context, const char *exten, int priority);
+
+/*!@}*/
+
 #endif /* _ASTERISK_JSON_H */