update Proc#lambda? doc.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@14579 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

proc.c

@@ -115,8 +115,11 @@ proc_clone(VALUE self)
  * Such procs are typically generated by lambda.
  *
  *   lambda {}.lambda?          => true
+ *   lambda {|a,b| [a,b]}.call(1,2,3)   => ArgumentError
  *
  *   proc {}.lambda?            => false
+ *   proc {|a,b| [a,b]}.call(1,2,3)     => [1,2]
+ *
  *   Proc.new {}.lambda?        => false
  *
  *   def m() end
@@ -124,10 +127,11 @@ proc_clone(VALUE self)
  *
  *   def n(&b) b.lambda? end
  *   n {}                       => false
- *   n(&lambda {})              => true
- *   n(&method(:m))             => true
  *   n(&proc {})                => false
  *   n(&Proc.new {})            => false
+ *   n(&lambda {})              => true
+ *   n(&method(:m))             => true
+ *   n(&method(:m)).to_proc     => true
  *
  */