gas: make NO_LISTING work again

Presumably since no target enables this and there's also no configure
control, builds with NO_LISTING defined didn't really work anymore.
Convert fallback functions to macros and add #ifndef in a few places.
(Behavior is different for affected command line options vs directives:
The former are rejected as unrecognized, while the latter are silently
ignored. I think that's fair enough.)

gas/listing.c

@@ -1658,58 +1658,4 @@ listing_source_file (const char *file)
     listing_tail->hll_file = file_info (file);
 }
 
-#else
-
-/* Dummy functions for when compiled without listing enabled.  */
-
-void
-listing_list (int on)
-{
-  s_ignore (0);
-}
-
-void
-listing_eject (int ignore)
-{
-  s_ignore (0);
-}
-
-void
-listing_psize (int ignore)
-{
-  s_ignore (0);
-}
-
-void
-listing_nopage (int ignore)
-{
-  s_ignore (0);
-}
-
-void
-listing_title (int depth)
-{
-  s_ignore (0);
-}
-
-void
-listing_file (const char *name)
-{
-}
-
-void
-listing_newline (char *name)
-{
-}
-
-void
-listing_source_line (unsigned int n)
-{
-}
-
-void
-listing_source_file (const char *n)
-{
-}
-
 #endif