patch 8.1.1558: popup_menu() and popup_filter_menu() are not implemented yet

Problem:    Popup_menu() and popup_filter_menu() are not implemented yet.
Solution:   Implement the functions. Fix that centering didn't take the border
            and padding into account.
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 8c8bb4d..b98c7e7 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -816,10 +816,12 @@
     {"popup_close",	1, 2, f_popup_close},
     {"popup_create",	2, 2, f_popup_create},
     {"popup_dialog",	2, 2, f_popup_dialog},
+    {"popup_filter_menu", 2, 2, f_popup_filter_menu},
     {"popup_filter_yesno", 2, 2, f_popup_filter_yesno},
     {"popup_getoptions", 1, 1, f_popup_getoptions},
     {"popup_getpos",	1, 1, f_popup_getpos},
     {"popup_hide",	1, 1, f_popup_hide},
+    {"popup_menu",	2, 2, f_popup_menu},
     {"popup_move",	2, 2, f_popup_move},
     {"popup_notification", 2, 2, f_popup_notification},
     {"popup_settext",	2, 2, f_popup_settext},