Version 0.2.5.2 - 2005/03/25
UA library:
- Major modification in dialog callbacks, now high level callbacks such as
  on_calling(), on_incoming(), on_provisional(), on_established(), and
  on_disconnected() are provided instead of just one callback (on_event()).
- Added pjsip_dlg_disconnect() which should handle all cases of disconnection
  such as sending CANCEL, sending BYE, or sending final response to INVITE.
- Added and updated doxygen comments.
- Renamed: pjsip_dialog_xxx --> pjsip_dlg_xxx

New:
- PJSIP Auth library, which supports digest scheme.
- Only client functionality is present at the moment.

PJSUA:
- Remove callgen feature, as it makes the application complicated.
  Will move it to different application, to make way for more sophisticated
  call generator.
- Support the new callback framework.
- As the result, it's lots simpler now. Just one file: main.c
- Support the new digest authentication (UAC only).

SIP core:
- Added PJSIP_EVENT_BEFORE_TX, triggered by transaction before sending
  outgoing messages (including retransmission). Application can use this event
  (via dialog callback) to modify the message before transmission (such as
  adding authorization headers, SDP body, etc.).
- Added general purpose function to print text body. Don't need to write
  the same function over and over again.
- Move constant strings in parser to public/extern, just in case other
  part of the library need to use them.

PJMEDIA:
- Protect against NULL in destroy session.

Misc:
- Added pjproject solution/workspace project to build everything.
- Rename build output directory x_Win32_x --> x_vc7_x or x_vc6_x, also
  libraries/exes naming includes _vc7_ or _vc6_ now, to support building
  the project on different IDEs on the same project directory tree.
- Renamed pjsip_test_core --> pjsip_core_test.
- Renamed pjaudio_tool --> pjmedia_audio_tool.
- Renamed sdp_test --> pjsdp_test
- PJLIB test: added second pool test after new/malloc test to show even more
  speed difference (9x faster than new/malloc).
- Renamed README.txt --> INSTALL.txt