patch 8.1.1713: highlighting cursor line only works with popup_menu()

Problem:    Highlighting cursor line only works with popup_menu().
Solution:   Add the "cursorline" property. (Naruhiko Nishino, closes #4671)
diff --git a/src/vim.h b/src/vim.h
index 410d9d7..452a9b9 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -617,6 +617,7 @@
 #define POPF_IS_POPUP	1	// this is a popup window
 #define POPF_HIDDEN	2	// popup is not displayed
 #define POPF_HANDLED	4	// popup was just redrawn or filtered
+#define POPF_CURSORLINE	8	// popup is highlighting at the cursorline
 #ifdef FEAT_TEXT_PROP
 # define WIN_IS_POPUP(wp) ((wp)->w_popup_flags != 0)
 #else