patch 8.1.1993: more functions can be used as methods

Problem:    More functions can be used as methods.
Solution:   Make various functions usable as a method.
diff --git a/src/testdir/test_cursor_func.vim b/src/testdir/test_cursor_func.vim
index fbe7be7..4fc28c9 100644
--- a/src/testdir/test_cursor_func.vim
+++ b/src/testdir/test_cursor_func.vim
@@ -87,7 +87,7 @@
   call assert_equal({'row': winrow,
 	\ 'col': wincol + 13,
 	\ 'curscol': wincol + 13,
-	\ 'endcol': wincol + 13}, screenpos(winid, 1, 7))
+	\ 'endcol': wincol + 13}, winid->screenpos(1, 7))
   call assert_equal({'row': winrow + 2,
 	\ 'col': wincol + 1,
 	\ 'curscol': wincol + 1,