Function loadfunc

** Try to find a load function for module 'modname' at file 'filename'. ** First, change '.' to '_' in 'modname'; then, if 'modname' has ** the form X-Y (that is, it has an "ignore mark"), build a function ** name "luaopen_X" and look for it. (For compatibility, if that ** fails, it also tries "luaopen_Y".) If there is no ignore mark, ** look for a function named "luaopen_modname". */