vim-patch:8.1.1920: cannot always close a popup when filter consumes all events

Problem:    Cannot close a popup by the X when a filter consumes all events.
Solution:   Check for a click on the close button before invoking filters.
            (closes vim/vim#4858)

f63962378d

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/mouse.c

@@ -1262,7 +1262,8 @@ retnomove:
     return IN_UNKNOWN;
   }
 
-  // find the window where the row is in
+  // find the window where the row is in and adjust "row" and "col" to be
+  // relative to top-left of the window
   win_T *wp = mouse_find_win(&grid, &row, &col);
   if (wp == NULL) {
     return IN_UNKNOWN;