patch 8.1.2407: proto files, dependencies and build instructions outdated

Problem:    proto file, dependenciess and Build instructions outdated.
Solution:   Update proto files, dependencies and build instructions.
diff --git a/src/proto/popupwin.pro b/src/proto/popupwin.pro
index dafe657..11db362 100644
--- a/src/proto/popupwin.pro
+++ b/src/proto/popupwin.pro
@@ -49,8 +49,8 @@
 void may_update_popup_mask(int type);
 void update_popups(void (*win_update)(win_T *wp));
 int set_ref_in_popups(int copyID);
-win_T *popup_find_preview_window(void);
 int popup_is_popup(win_T *wp);
+win_T *popup_find_preview_window(void);
 win_T *popup_find_info_window(void);
 void f_popup_findinfo(typval_T *argvars, typval_T *rettv);
 void f_popup_findpreview(typval_T *argvars, typval_T *rettv);