0.5.2 Minor feature release

Release 0.5.2 introduces optional _get suffix to reader methods. By using flatcc -g only _get methods are valid. This removes potential name conficts for some field names. 0.5.2 also introduces the long awaited clone operation for tables and vectors. A C++ smoketest was added to reduce the number void pointer assignment errors that kept sneaking in. The runtime library now needs an extra file refmap.c.