fix(window): remove useless operator= and add default copy cstr (#1729)

Fixes compilation under GCC 9

The default copy constructor implicit generation is deprecated by C++ standard.

The window& operator=(const xcb_window_t win); operator seems to be useless.

Fixes #1728
Ref polybar/xpp#16

include/x11/window.hpp

@@ -12,10 +12,9 @@ class connection;
 
 class window : public xpp::window<connection&> {
  public:
+  window(const window&) = default;
   using xpp::window<class connection&>::window;
 
-  window& operator=(const xcb_window_t win);
-
   window reconfigure_geom(unsigned short int w, unsigned short int h, short int x = 0, short int y = 0);
   window reconfigure_pos(short int x, short int y);
   window reconfigure_struts(unsigned short int w, unsigned short int h, short int x, bool bottom = false);

src/x11/window.cpp

@@ -7,11 +7,6 @@
 
 POLYBAR_NS
 
-window& window::operator=(const xcb_window_t win) {
-  resource(connection(), win);
-  return *this;
-}
-
 /**
  * Reconfigure the window geometry
  */