Optimization: Cache the relative filename when creating code objects.
Optimization: Cache the relative filename when creating code objects.

* This speeds up the init of modules with many functions, which used
  to independently call MAKE_RELATIVE_PATH with the same argument
  over and over. Now it's only called once per module.

* Now that all "__file__" values are relative, this affected construct
  tests, and indicated larger differences caused by functions being
  defined or not than necessary.

wfxiang08/Nuitka,kayhayen/Nuitka,tempbottle/Nuitka,wfxiang08/Nuitka,tempbottle/Nuitka,wfxiang08/Nuitka,kayhayen/Nuitka,tempbottle/Nuitka,wfxiang08/Nuitka,kayhayen/Nuitka,tempbottle/Nuitka,kayhayen/Nuitka