patch 8.2.0871: cannot use getmarklist() as a method

Problem:    Cannot use getmarklist() as a method.
Solution:   Make getmarklist() work as a method.  Add one to the column
            number to match getpos(). (Yegappan Lakshmanan, closes #6176)
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index fb0b2a7..7582a27 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -5385,6 +5385,8 @@
 		Refer to |getpos()| for getting information about a specific
 		mark.
 
+		Can also be used as a |method|: >
+			GetBufnr()->getmarklist()
 
 getmatches([{win}])					*getmatches()*
 		Returns a |List| with all matches previously defined for the