This cleans up the constructor methods for the OpenCL wrapper
classes and unifies the API used for creating a wrapper class
object from the underlying OpenCL objects.
Now, every wrapper class has a constructor taking the OpenCL
object and an optional boolean retain parameter which indicates
whether the constructor should increment the reference count.
This remove the enqueue_wait_for_event() method from the
command_queue class as the clEnqueueWaitForEvents() function
has been deprecated in OpenCL 1.2.
This implements the merge() algorithm which merges two
ranges of sorted values into a single sorted range.
The current implementation uses a simple serial merge
algorithm. A GPU optimized version is coming soon.
