patch 8.1.1645: cannot use a popup window for a balloon

Problem:    Cannot use a popup window for a balloon.
Solution:   Add popup_beval().  Add the "mousemoved" property.  Add the
            screenpos() function.
diff --git a/src/proto/beval.pro b/src/proto/beval.pro
index 2be64a0..0238907 100644
--- a/src/proto/beval.pro
+++ b/src/proto/beval.pro
@@ -1,5 +1,6 @@
 /* beval.c */
 int get_beval_info(BalloonEval *beval, int getword, win_T **winp, linenr_T *lnump, char_u **textp, int *colp);
+int find_word_under_cursor(int mouserow, int mousecol, int getword, int flags, win_T **winp, linenr_T *lnump, char_u **textp, int *colp);
 void post_balloon(BalloonEval *beval, char_u *mesg, list_T *list);
 int can_use_beval(void);
 void general_beval_cb(BalloonEval *beval, int state);
diff --git a/src/proto/move.pro b/src/proto/move.pro
index ed45c4d..c2ec8d5 100644
--- a/src/proto/move.pro
+++ b/src/proto/move.pro
@@ -27,6 +27,7 @@
 int win_col_off2(win_T *wp);
 int curwin_col_off2(void);
 void curs_columns(int may_scroll);
+void f_screenpos(typval_T *argvars, typval_T *rettv);
 void scrolldown(long line_count, int byfold);
 void scrollup(long line_count, int byfold);
 void check_topfill(win_T *wp, int down);
diff --git a/src/proto/popupwin.pro b/src/proto/popupwin.pro
index a251f9a..7733368 100644
--- a/src/proto/popupwin.pro
+++ b/src/proto/popupwin.pro
@@ -11,7 +11,9 @@
 void f_popup_clear(typval_T *argvars, typval_T *rettv);
 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_for_mouse_click(win_T *wp);
+void popup_handle_mouse_moved(void);
 void f_popup_filter_menu(typval_T *argvars, typval_T *rettv);
 void f_popup_filter_yesno(typval_T *argvars, typval_T *rettv);
 void f_popup_dialog(typval_T *argvars, typval_T *rettv);