patch 8.1.1834: cannot use a lambda as a method

Problem:    Cannot use a lambda as a method.
Solution:   Implement ->{lambda}(). (closes #4768)
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 2f35c7c..981121f 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1217,7 +1217,8 @@
 When expr8 is a |Funcref| type variable, invoke the function it refers to.
 
 
-expr8->name([args])	method call			*method*
+expr8->name([args])	method call			*method* *->*
+expr8->{lambda}([args])
 
 For methods that are also available as global functions this is the same as: >
 	name(expr8 [, args])
@@ -1227,6 +1228,9 @@
 next method: >
 	mylist->filter(filterexpr)->map(mapexpr)->sort()->join()
 <
+Example of using a lambda: >
+	GetPercentage->{x -> x * 100}()->printf('%d%%')
+
 							*E274*
 "->name(" must not contain white space.  There can be white space before the
 "->" and after the "(", thus you can split the lines like this: >