patch 8.1.1438: some commands cause trouble in a popup window

Problem:    Some commands cause trouble in a popup window.
Solution:   Add NOT_IN_POPUP_WINDOW.
diff --git a/src/window.c b/src/window.c
index e73a9f4..42689ee 100644
--- a/src/window.c
+++ b/src/window.c
@@ -87,7 +87,8 @@
 #endif
     char_u	cbuf[40];
 
-    Prenum1 = Prenum == 0 ? 1 : Prenum;
+    if (NOT_IN_POPUP_WINDOW)
+	return;
 
 #ifdef FEAT_CMDWIN
 # define CHECK_CMDWIN \
@@ -102,6 +103,8 @@
 # define CHECK_CMDWIN do { /**/ } while (0)
 #endif
 
+    Prenum1 = Prenum == 0 ? 1 : Prenum;
+
     switch (nchar)
     {
 /* split current window in two parts, horizontally */
@@ -732,6 +735,9 @@
     int
 win_split(int size, int flags)
 {
+    if (NOT_IN_POPUP_WINDOW)
+	return FAIL;
+
     /* When the ":tab" modifier was used open a new tab page instead. */
     if (may_open_tabpage() == OK)
 	return OK;
@@ -1509,7 +1515,9 @@
     win_T	*wp2;
     int		temp;
 
-    if (ONE_WINDOW)	    /* just one window */
+    if (NOT_IN_POPUP_WINDOW)
+	return;
+    if (ONE_WINDOW)	    // just one window
     {
 	beep_flush();
 	return;
@@ -2363,6 +2371,9 @@
     tabpage_T   *prev_curtab = curtab;
     frame_T	*win_frame = win->w_frame->fr_parent;
 
+    if (NOT_IN_POPUP_WINDOW)
+	return FAIL;
+
     if (last_window())
     {
 	emsg(_("E444: Cannot close last window"));
@@ -4221,6 +4232,8 @@
     win_T	*owp = curwin;
 #endif
 
+    if (NOT_IN_POPUP_WINDOW)
+	return;
     if (text_locked())
     {
 	beep_flush();