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_cmdline.vim b/src/testdir/test_cmdline.vim
index 6ed7848..26a50e0 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -672,7 +672,7 @@
   call assert_equal('"12ab', @:)
 
   " setcmdpos() returns 1 when not editing the command line.
-  call assert_equal(1, setcmdpos(3))
+  call assert_equal(1, 3->setcmdpos())
 endfunc
 
 func Test_cmdline_overstrike()