Remove -dump_xml command line option

This has never been documented aside from a passing mention in
CHANGES which doesn't say what it actually does, and its naming doesn't
match the scheme that SWIG uses.

The same result can be achieved on many platforms by using
`-xmlout /dev/stdout`, or you can just write the output to a file.

CHANGES.current

@@ -104,6 +104,7 @@ Version 4.2.0 (in progress)
 	    -dump_top		Use -debug-top 4 instead.
 	    -dump_tree		Use -debug-top 4 instead.
 	    -dump_typedef	Use -debug-typedef instead.
+	    -dump_xml		Use -xmlout /dev/stdout instead.
 	    -make_default	On by default since SWIG 1.3.7 (2001-09-03).
 	    -makedefault	On by default since SWIG 1.3.7 (2001-09-03).
 	    -no_default		Use %nodefaultctor/%nodedefaultdtor instead.

Source/Modules/main.cxx

@@ -194,7 +194,6 @@ static int dump_lang_symbols = 0;
 static int dump_tags = 0;
 static int dump_module = 0;
 static int dump_top = 0;
-static int dump_xml = 0;
 static int dump_typedef = 0;
 static int dump_classes = 0;
 static int werror = 0;
@@ -766,11 +765,7 @@ static void getoptions(int argc, char *argv[]) {
 	} else {
 	  Swig_arg_error();
 	}
-      } else if (strcmp(argv[i], "-dump_xml") == 0) {
-	dump_xml = 1;
-	Swig_mark_arg(i);
       } else if (strcmp(argv[i], "-xmlout") == 0) {
-	dump_xml = 1;
 	Swig_mark_arg(i);
 	if (argv[i + 1]) {
 	  xmlout = NewString(argv[i + 1]);
@@ -1257,7 +1252,7 @@ int SWIG_main(int argc, char *argv[], const TargetLanguageModule *tlm) {
       Printf(stdout, "debug-module stage 4\n");
       Swig_print_tree(Getattr(top, "module"));
     }
-    if (dump_xml && top) {
+    if (xmlout && top) {
       delete lang;
       lang = 0;
       Swig_print_xml(top, xmlout);

Source/Modules/xml.cxx

@@ -285,14 +285,10 @@ void Swig_print_xml(Node *obj, String *filename) {
   XML xml;
   xmllite = 1;
 
-  if (!filename) {
-    out = stdout;
-  } else {
-    out = NewFile(filename, "w", SWIG_output_files());
-    if (!out) {
-      FileErrorDisplay(filename);
-      Exit(EXIT_FAILURE);
-    }
+  out = NewFile(filename, "w", SWIG_output_files());
+  if (!out) {
+    FileErrorDisplay(filename);
+    Exit(EXIT_FAILURE);
   }
 
   Printf(out, "<?xml version=\"1.0\" ?> \n");