Remove remaining code to support macos9

This OS has been unsupported for over 20 years.  We stopped providing
macswig builds more than 20 years ago too:

https://sourceforge.net/projects/swig/files/macswig/

The required SIOUX library doesn't seem to be available anywhere
now either.

Closes #2323

Source/Modules/swigmain.cxx

@@ -84,11 +84,6 @@ static TargetLanguageModule modules[] = {
   {NULL, NULL, NULL, Disabled}
 };
 
-#ifdef MACSWIG
-#include <console.h>
-#include <SIOUX.h>
-#endif
-
 //-----------------------------------------------------------------
 // main()
 //
@@ -222,11 +217,6 @@ int main(int margc, char **margv) {
   SWIG_merge_envopt(getenv("SWIG_FEATURES"), margc, margv, &argc, &argv);
   merge_options_files(&argc, &argv);
 
-#ifdef MACSWIG
-  SIOUXSettings.asktosaveonclose = false;
-  argc = ccommand(&argv);
-#endif
-
   Swig_init_args(argc, argv);
 
   /* Get options */