patch 8.1.1921: 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_search.vim b/src/testdir/test_search.vim
index 604f3c2..7c30a1a 100644
--- a/src/testdir/test_search.vim
+++ b/src/testdir/test_search.vim
@@ -1303,7 +1303,7 @@
 
   call cursor(1, 1)
   let @/ = 'foo'
-  let pat = escape(@/, '()*?'. '\s\+')
+  let pat = @/->escape('()*?'. '\s\+')
   let g:a = execute(':unsilent :norm! n')
   call assert_match(pat, g:a)