* lib/e2mmap.rb: remove needless instance variables.
* lib/irb.rb: ditto.
* lib/irb/**/*.rb: ditto.
* lib/shell.rb: ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47266 b2dd03c8-39d4-4d8f-98ff-823fe69b080e