patch 8.1.2011: more functions can be used as methods

Problem:    More functions can be used as methods.
Solution:   Make various functions usable as a method.  Make the window
            command test faster.
diff --git a/src/testdir/test_timers.vim b/src/testdir/test_timers.vim
index 3eebad6..261be27 100644
--- a/src/testdir/test_timers.vim
+++ b/src/testdir/test_timers.vim
@@ -251,7 +251,7 @@
 endfunc
 
 func Interrupt(timer)
-  call test_feedinput("\<C-C>")
+  eval "\<C-C>"->test_feedinput()
 endfunc
 
 func Test_timer_peek_and_get_char()