message: Rename GPU CMAKE build options
diff: # * provided "as is" without express or implied warranty. *
  # **************************************************************************
  -option(HLT_CUDA "Build HLT GPU tracker using CUDA" OFF)
  -option(HLT_OPENCL "Build HLT GPU tracker using OpenCL" OFF)
  +option(ENABLE_CUDA "Build HLT GPU tracker using CUDA" OFF)
  +option(ENABLE_OPENCL "Build HLT GPU tracker using OpenCL" OFF)
  add_definitions(-Duse_aliroot -DUSE_ROOT -DROWHOUGHPARAMS)
  