Suggestions for resolving memory leaks

These changes are suggestions for resolving memory leaks
And the some buffers, which are allocated by "pocl_aligned_malloc", are
deallocated by "free". It makes some troubles. I also suggest all malloc
and calloc should be changed to "pocl_aligned_malloc" also "free" should
be changed to "pocl_aligned_free"
In case of some functions, which have the prefix "clEnqueue". Those functions handle the command queue. But the only function clEnqueueNDRangeKernel includes the clRetainCommandQueue. command queue is combined event and If even is released command queue can be released in  final. please see the my modification in clFinish