Refactor: move makeParameterName() to common Language base class.

This method was duplicated more or less identically for 4 languages and will
be needed for another one soon, so put it in the base class from which it can
be simply reused instead.

No changes in the program behaviour whatsoever.

Source/Modules/lang.cxx

@@ -3499,6 +3499,44 @@ int Language::is_smart_pointer() const {
   return SmartPointer;
 }
 
+/* -----------------------------------------------------------------------------
+ * Language::makeParameterName()
+ *
+ * Inputs: 
+ *   n - Node
+ *   p - parameter node
+ *   arg_num - parameter argument number
+ *   setter  - set this flag when wrapping variables
+ * Return:
+ *   arg - a unique parameter name
+ * ----------------------------------------------------------------------------- */
+String *Language::makeParameterName(Node *n, Parm *p, int arg_num, bool setter) const {
+
+  String *arg = 0;
+  String *pn = Getattr(p, "name");
+
+  // Use C parameter name unless it is a duplicate or an empty parameter name
+  int count = 0;
+  ParmList *plist = Getattr(n, "parms");
+  while (plist) {
+    if ((Cmp(pn, Getattr(plist, "name")) == 0))
+      count++;
+    plist = nextSibling(plist);
+  }
+  String *wrn = pn ? Swig_name_warning(p, 0, pn, 0) : 0;
+  arg = (!pn || (count > 1) || wrn) ? NewStringf("arg%d", arg_num) : Copy(pn);
+
+  if (setter && Cmp(arg, "self") != 0) {
+    // Some languages (C#) insist on calling the input variable "value" while
+    // others (D, Java) could, in principle, use something different but this
+    // would require more work, and so we just use "value" for them too.
+    Delete(arg);
+    arg = NewString("value");
+  }
+
+  return arg;
+}
+
 /* -----------------------------------------------------------------------------
  * Language::()
  * ----------------------------------------------------------------------------- */