patch 8.2.4913: popup_hide() does not always have effect

Problem:    Popup_hide() does not always have effect.
Solution:   Add the POPF_HIDDEN_FORCE flag. (closes #10376)
diff --git a/src/vim.h b/src/vim.h
index 9e34c2e..f17da41 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -631,15 +631,16 @@
 // Values for w_popup_flags.
 #define POPF_IS_POPUP	0x01	// this is a popup window
 #define POPF_HIDDEN	0x02	// popup is not displayed
-#define POPF_CURSORLINE	0x04	// popup is highlighting at the cursorline
-#define POPF_ON_CMDLINE	0x08	// popup overlaps command line
-#define POPF_DRAG	0x10	// popup can be moved by dragging border
-#define POPF_DRAGALL	0x20	// popup can be moved by dragging everywhere
-#define POPF_RESIZE	0x40	// popup can be resized by dragging
-#define POPF_MAPPING	0x80	// mapping keys
-#define POPF_INFO	0x100	// used for info of popup menu
-#define POPF_INFO_MENU	0x200	// align info popup with popup menu
-#define POPF_POSINVERT	0x400	// vertical position can be inverted
+#define POPF_HIDDEN_FORCE 0x04	// popup is explicitly set to not be displayed
+#define POPF_CURSORLINE	0x08	// popup is highlighting at the cursorline
+#define POPF_ON_CMDLINE	0x10	// popup overlaps command line
+#define POPF_DRAG	0x20	// popup can be moved by dragging border
+#define POPF_DRAGALL	0x40	// popup can be moved by dragging everywhere
+#define POPF_RESIZE	0x80	// popup can be resized by dragging
+#define POPF_MAPPING	0x100	// mapping keys
+#define POPF_INFO	0x200	// used for info of popup menu
+#define POPF_INFO_MENU	0x400	// align info popup with popup menu
+#define POPF_POSINVERT	0x800	// vertical position can be inverted
 
 // flags used in w_popup_handled
 #define POPUP_HANDLED_1	    0x01    // used by mouse_find_win()