ui_window - add destroy function callback

ui/drivers/null/ui_null_window.c

@@ -21,12 +21,17 @@
 
 #include "../../ui_companion_driver.h"
 
+void ui_window_null_destroy(void *data)
+{
+}
+
 static void ui_window_null_set_visible(void *data,
         bool set_visible)
 {
 }
 
 const ui_window_t ui_window_null = {
+   ui_window_null_destroy,
    ui_window_null_set_visible,
    "null",
 };

ui/drivers/win32/ui_win32_window.c

@@ -58,6 +58,7 @@ void ui_window_win32_set_visible(void *data,
 }
 
 const ui_window_t ui_window_win32 = {
+   ui_window_win32_destroy,
    ui_window_win32_set_visible,
    "win32",
 };

ui/ui_companion_driver.h

@@ -33,6 +33,7 @@ RETRO_BEGIN_DECLS
 
 typedef struct ui_window
 {
+   void (*destroy)(void *data);
    void (*set_visible)(void *data, bool visible);
    const char *ident;
 } ui_window_t;