in the kernel we need:
* SLEvaluatorCompiled in SLP-...{hpp,cpp}
* rawSLEvaluatorCompiled in engine.dd...
* modify rawSLEvaluatorEvaluate (to call a fn from dll)

in the front:
* makeSLProgram should have an option "compiled"=>false
  * store cCode in SLProgram
* modify rawSLEvaluatorK for the case "compiled"=>true
  * create dll (use temporaryFileName) 
  * call rawSLEvaluatorCompiled