Added /clear command to clear current window

src/ui/ui.h

@@ -99,6 +99,7 @@ void title_bar_draw(void);
 
 // current window actions
 void win_current_close(void);
+void win_current_clear(void);
 int win_current_is_console(void);
 int win_current_is_chat(void);
 int win_current_is_groupchat(void);