webos-image: libpbnjson=18

:Release Notes:
1133e99 Reduce memory usage of JSON values
94ef0a5 Remove memory errors from unit tests
3eefb10 Add API to verify jvalue against schema
2ebbe10 Fix public API error checking
bef4f4c Refactor jobject to use GHashTable
71a41e0 Fix cosmetic whitespace style

:Detailed Notes:
Refactored to use GHashTable instead of a homebrew poor data structure
to store members of JSON object.
Fixed error checking in public API to prevent undefined behaviour.
Implemented functions to validate a JSON object against a schema,
which allowed to decouple serialization from validation.
Redesigned the jvalue struct to avoid relying on union, thus improving
memory footprint drastically.
Finally, the unit tests have been fixed to get rid of memory leaks.

:Testing Performed:
Unit tests were passed.
Unit tests were run with detection of memory errors.
MiniBAT results attached to the task in Jira.

:QA Notes:

:Issues Addressed:
[GF-10385] CCC: libpbnjson=18
[GF-2836] Validation of json objects against schemas in pbnjson
[GF-6969] Refactor jobject to use GHashTable
[GF-8147] libpbnjson: Check and fix type information in all public API
[GF-8743] Improve memory usage of jvalue
[GF-9794] Remove memory errors from internal unit tests

Open-webOS-DCO-1.0-Signed-off-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>

Change-Id: Id0fcd7c5d94bf89c22ab982b93b16393619dbfe7
Reviewed-on: https://g2g.palm.com/2897
Reviewed-by: Build Verification
Tested-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Reviewed-by: Keith Derrick <keith.derrick@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>