Require console for UI_Console (ruby#15)

Fixes scenarios where session isn't started immediately.

    require 'debug/session'
    DEBUGGER__.console # raises NameError

Author: adam12

lib/debug/session.rb

@@ -936,6 +936,7 @@ def self.require_location
   end
 
   def self.console
+    require_relative 'console'
     initialize_session UI_Console.new
 
     @prev_handler = trap(:SIGINT){