New log features: indentation and thread switching indication

[bennylp]

1. Indentation

Indentation of log message to show function depth. Example:

21:13:35.787   pjsua_call.c  Answering call 1: code=200
21:13:35.787  pjsua_media.c  ...Call 1: updating media..
21:13:35.787  pjsua_media.c  .....Media session call01:0 is destroyed
21:13:35.787  pjsua_media.c  ....Audio channel update..
21:13:35.787  strm0x22f04d8  .....VAD temporarily disabled
21:13:35.788  strm0x22f04d8  .....Encoder stream started
21:13:35.788  strm0x22f04d8  .....Decoder stream started
21:13:35.788    pjsua_app.c  ...Call 1 media 0 [type=audio], status is Active
21:13:35.788  pjsua_media.c  ...Conf disconnect: 2 -x- 0
21:13:35.788  pjsua_media.c  ...Conf connect: 3 --> 0
21:13:35.788  pjsua_media.c  ...Conf connect: 0 --> 3

Use pj_log_push_indent() and pj_log_pop_indent() to use this new feature. The PJ_LOG_HAS_INDENT must be set in the log decoration flag (it is set by default by PJSUA-LIB).

Also two new macros to customize the behavior: PJ_LOG_INDENT_SIZE, and PJ_LOG_INDENT_CHAR.

2. Thread Switch Indication

An exclamation mark will be placed before the log message if the caller thread is different than the previous message.

Example:

21:13:35.788  strm0x22f04d8  .....Decoder stream started
21:13:35.788   udp0x22deab0 !Remote RTCP address switched to 10.0.0.2:40003
21:13:35.788  pjsua_media.c !.....Audio updated, stream #0: speex (sendrecv)
21:13:35.788    pjsua_app.c  ...Call 1 media 0 [type=audio], status is Active
21:13:35.788  pjsua_media.c  ...Conf disconnect: 2 -x- 0

This feature is controlled by the new PJ_LOG_HAS_THREAD_SWC log decor. It is set by default by PJSUA-LIB.