In c-\(go-\)?-\(up-\|down-\)?list-\(forward\|backward\) check limit isn't nil

In c-\(go-\)?-\(up-\|down-\)?list-\(forward\|backward\) check limit isn't nil

Check the limit both at macro expansion time (for a hard coded nil) and at run
time in the generated code.  Tidy up these macros generally.

* lisp/progmodes/cc-defs.el (c-safe-scan-lists): Check `limit' is present and
not identically nil before generating a narrow-to-region call.  Generate code
to check `limit' is not nil at run time.
(c-go-list-forward, c-go-list-backward): Remove the generation of redundant
narrow-to-region, instead calling c-safe-scan-lists directly.
(c-go-up-list-forward, c-go-up-list-backward, c-go-down-list-forward)
(c-go-down-list-backward): Invoke the corresponding macros without the "go-"
to determine the destination position instead of generating a redundant
narrow-to-region.