add support for yajl 2.0+

- detect pre yajl_version.h
- support for both yajl version
- use size_t in jtypes.h

Open-webOS-DCO-1.0-Signed-off-by: Nikolay Orliuk <norluk@luxoft.com>
Change-Id: I0846ba87efb52f5ca326dd4ee5cb9d46e65c0d2c