fix PJ_LOG_DBG, logging stub and weak magic

:Release Notes:
Made test run successfully without linking with pmloglib

:Detailed Notes:
- Moved liblog.c to be compiled directly as a part of shared library.
  Otherwise unexplained segfault happens when it comes from shared
  library jvalue.
- Fixed usage and define of PJ_LOG_DBG macro.
- Fixed stub for _PmLogMsgKV

:Testing Performed:
Unit-tests.

:QA Notes:

:Issues Addressed:
[BHV-8] pbnjson: Refactor logging to use pmloglib

Open-webOS-DCO-1.0-Signed-off-by: Nikolay Orliuk <nikolay.orliuk@lge.com>

Change-Id: I6ffc5c1af487b58db058665077622e70f2c9c008
Reviewed-on: https://g2g.palm.com/5174
Reviewed-by: DCO Verification
Reviewed-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Tested-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>