Add missing *public* methods of Fl_Single_Window

- void make_current()
- void flush()

FL/Fl_Single_Window.H

@@ -1,7 +1,7 @@
 //
 // Single-buffered window header file for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 1998-2015 by Bill Spitzak and others.
+// Copyright 1998-2024 by Bill Spitzak and others.
 //
 // This library is free software. Distribution and use rights are outlined in
 // the file "COPYING" which should have been included with this file.  If this
@@ -32,8 +32,8 @@
 class FL_EXPORT Fl_Single_Window : public Fl_Window {
 public:
   void show() FL_OVERRIDE;
-  /** Same as Fl_Window::show(int a, char **b) */
-  void show(int a, char **b) {Fl_Window::show(a,b);}
+  /** Same as Fl_Window::show(int argc, char **argv) */
+  void show(int argc, char **argv) { Fl_Window::show(argc, argv);}
 
    /**
     Creates a new Fl_Single_Window widget using the given
@@ -46,6 +46,16 @@ public:
     position, size, and label (title) string.
   */
   Fl_Single_Window(int X, int Y, int W, int H, const char *l=0);
+
+  /**
+    Same as Fl_Window::make_current()
+  */
+  void make_current() { Fl_Window::make_current(); }
+
+  /**
+    Same as Fl_Window::flush()
+  */
+  void flush() { Fl_Window::flush(); }
 };
 
 #endif