Add comparison functions to JSON C API

:Release Notes:
Implemented jvalue_equal comparison function for JSON value in C API.

:Detailed Notes:

:Testing Performed:
Unit test with valgrind

:QA Notes:

:Issues Addressed:
[GF-44132] pbnjson: Expand jvalue C API to support JSON values
           comparison

Open-webOS-DCO-1.0-Signed-off-by: Mykola Kryvonos <mykola.kryvonos@lge.com>

Change-Id: I68200e9b6c16bfc01395976175a191f1b752d6c0
Reviewed-on: https://g2g.palm.com/3752
Reviewed-by: Build Verification
Reviewed-by: Mykola Kryvonos <mykola.kryvonos@lge.com>
Tested-by: Mykola Kryvonos <mykola.kryvonos@lge.com>
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Reviewed-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>