patch 8.2.0191: cannot put a terminal in a popup window

Problem:    Cannot put a terminal in a popup window.
Solution:   Allow opening a terminal in a popup window.  It will always have
            keyboard focus until closed.
diff --git a/src/proto/popupwin.pro b/src/proto/popupwin.pro
index 11db362..bfbd883 100644
--- a/src/proto/popupwin.pro
+++ b/src/proto/popupwin.pro
@@ -19,6 +19,7 @@
 void f_popup_create(typval_T *argvars, typval_T *rettv);
 void f_popup_atcursor(typval_T *argvars, typval_T *rettv);
 void f_popup_beval(typval_T *argvars, typval_T *rettv);
+void popup_close_with_retval(win_T *wp, int retval);
 void popup_close_for_mouse_click(win_T *wp);
 void popup_handle_mouse_moved(void);
 void f_popup_filter_menu(typval_T *argvars, typval_T *rettv);
@@ -41,6 +42,7 @@
 void f_popup_locate(typval_T *argvars, typval_T *rettv);
 void f_popup_getoptions(typval_T *argvars, typval_T *rettv);
 int error_if_popup_window(void);
+int error_if_term_popup_window(void);
 void popup_reset_handled(int handled_flag);
 win_T *find_next_popup(int lowest, int handled_flag);
 int popup_do_filter(int c);