Added more device checks
Added more device checks

* added checks similar to those from the MMCL project, to check whether the
device tested supports the required work-group dimensions and sizes
* plugged a memory leak
* removed some obsolete code

ChrisLidbury/CLSmith,ChrisLidbury/CLSmith,ChrisLidbury/CLSmith,ChrisLidbury/CLSmith,ChrisLidbury/CLSmith