this fixes some compilation issues with libosmocore under NuttX,
particularly as some #defines are missing or some header files are
slightly different.
Sometimes a control interface command cannot be processed
and responded immediately, but we need to process it asynchronously.
In order to support this, we introduce the 'ctrl_cmd_def', which
represents such a deferred command. It is created by the service
implementing the command using ctrl_cmd_def_make(), and a response is
later sent using ctrl_cmd_def_send().
ctrl_cmd_def_is_zombie() must be called to handle the case where
the control connection has disconnected/died between receiving the
command and sending the response.
The control interface user now only has to register a very short
node lookup function callback. This function is optional, and only
required if hierarchical command lookup should be supported.
Instead of using one flat talloc context (and one that is specific to
openbsc), we should attach the objects to whatever parent context they
are being used in.
Harald Welte
Holger Hans Peter Freyther