Include the parsed XML tuple in the pjsip_pres_status, and include it in the pjsua_buddy_info in PJSUA-LIB (thanks Johan Lantz for the suggestion)

[bennylp]

Several enhancements on the presence body handling:

• include the full parsed XML tuple in pjsip_pres_status structure, as it may contain additional information for the application
• include pjsua_pres_status in pjsua_buddy_info so that this information is accessible by PJSUA-LIB application.
• add timestamp info in the outgoing PIDF. There may be case when subscriber receives PIDF with multiple tuples, and in this case it can use the timestamp to decide which tuple to use.