Support for SIP Message Summary/Message Waiting Indication (MWI, RFC 3842)

[bennylp]

Add support for MWI with the following specification:

• implement pjsip evsub package for MWI
• client and server support
• unsolicited MWI support (unsolicited means NOTIFY is sent without subscription)
• support in PJSUA-LIB
• NOTIFY message body is unprocessed; they will be given to app unparsed.

New files in pjsip-simple:

• include: mwi.h
• src: mwi.c

Support in PJSUA-LIB:

• add "mwi_enabled" field in pjsua account config
• add "on_mwi_info" callback
• if MWI subscription is terminated for some reason, PJSUA-LIB will renew periodically (PJSUA_PRES_TIMER timer)
• enable/handle unsolicited MWI by default

PJSUA application:

• new "---mwi" option
• print MWI info

[bennylp]

Implemented in r2968:

• PJSIP-SIMPLE:
  • implement MWI
• PJSUA-LIB:
  • added "mwi_enabled" flag in account config
  • added "on_mwi_info" callback
• pjsua app:
  • added "--mwi" option to enable MWI on account
  • added simple callback to log the NOTIFY message
• other:
  • added SIPp scenario files to simulate UAS side
• build:
  • added MWI support on VS6, VS2005, MMP, and Makefile

[bennylp]

In r2974:

• updated VS6 project with the (missing) mwi.[hc] files

[bennylp]

In r2976:

• added MWI support for Python

[bennylp]

In r3019:

• added support for Asterisk unsolicited MWI requests in pjsua application (new "--unsolicited-mwi" option)

[bennylp]

In r3021:

• undo r3019 which put unsolicited MWI support in pjsua app only
• put the unsolicited MWI support in PJSUA-LIB instead
• unsolicited MWI is by default enabled
• on_mwi_info() callback will be called just as the solicited MWI version