Nbody: Fix bug in CL simulation
Issue #94

    * The methods WebCLGLCommandQueue::enqueueAcquireGLObjects
     and WebCLGLCommandQueue::enqueueReleaseGLObjects was
     changed to receive a list of WebCLMemory objects instead one
     object. It is according WebCL especification

    Reviewed by: Andre Loureiro

    Signed-off-by: Alexandre Rocha<a.rocha@samsung.com>