APIs to facilitate pending processing of pjsip_rx_data

[bennylp]

Processing of incoming messages (i.e. pjsip_rx_data) is done in on_rx_request() and on_rx_response() callbacks of a pjsip module. These callbacks must return immediately so that the next incoming packet can be processed by transports. This is especially true for TCP and TLS transports, since one TCP transport (i.e. socket) can only have one pjsip_rx_data buffer.

Some modules may want to have longer time in processing the message, for example to perform database operations or to consult other servers. For this usage, we want to be able to return from the on_rx_xxx() callback immediately, and later resume distributing the pjsip_rx_data to pjsip modules when the database operation is done.

This ticket adds the following APIs to facilitate the above:

• pjsip_rx_data_clone(): clone rdata
• pjsip_rx_data_free_cloned(): free cloned rdata
• pjsip_endpt_process_rx_data(): distribute a (cloned) rdata to modules, specifying from which module the processing should start.

[nanang]

In r4275: APIs to facilitate pending processing of pjsip_rx_data.

[nanang]

In 4291:

Re #1590: Fixed compile error 'invalid conversion from pj_list_type*' to pjsip_module*' on Symbian (thanks Rubel for the report).

[nanang]

In 4295:

Re #1590: Fixed pjsip_rx_data_clone() when there are multiple instances of a single header type (thanks Mike Evans for the report and the fix).