prelude.rb: Binding#irb [ci skip]

* prelude.rb (Binding#irb): [EXPERIMENTAL] automatically require
  irb and run.  [ruby-core:78960] [Bug #13099]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57274 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/irb.rb

@@ -708,6 +708,7 @@ end
 
 class Binding
   # :nodoc:
+  undef irb if method_defined?(:irb)
   def irb
     IRB.setup(eval("__FILE__"))
     IRB::Irb.new(IRB::WorkSpace.new(self)).run(IRB.conf)

prelude.rb

@@ -133,3 +133,10 @@ class IO
     __write_nonblock(buf, exception)
   end
 end
+
+class Binding
+  def irb
+    require 'irb'
+    irb
+  end
+end