Suppress warnings

[pocke]

IRB displays warnings when it loads extensions.

$ RUBYOPT='-w -Ilib/' exe/irb -f -r irb/ext/history.rb
/home/pocke/ghq/github.com/ruby/irb/lib/irb/ext/history.rb:44: warning: method redefined; discarding old eval_history=
/home/pocke/ghq/github.com/ruby/irb/lib/irb/extend-command.rb:239: warning: previous definition of eval_history= was here
irb(main):001:0> 


$ RUBYOPT='-w -Ilib/' exe/irb -f -r irb/ext/use-loader.rb
/home/pocke/ghq/github.com/ruby/irb/lib/irb/ext/use-loader.rb:24: warning: method redefined; discarding old irb_load
/home/pocke/ghq/github.com/ruby/irb/lib/irb/extend-command.rb:142: warning: previous definition of irb_load was here
/home/pocke/ghq/github.com/ruby/irb/lib/irb/ext/use-loader.rb:28: warning: method redefined; discarding old irb_require
/home/pocke/ghq/github.com/ruby/irb/lib/irb/extend-command.rb:142: warning: previous definition of irb_require was here
/home/pocke/ghq/github.com/ruby/irb/lib/irb/ext/use-loader.rb:50: warning: method redefined; discarding old use_loader=
/home/pocke/ghq/github.com/ruby/irb/lib/irb/extend-command.rb:239: warning: previous definition of use_loader= was here
irb(main):001:0> 


$ RUBYOPT='-w -Ilib/' exe/irb -f -r irb/ext/save-history.rb
/home/pocke/ghq/github.com/ruby/irb/lib/irb/ext/save-history.rb:40: warning: method redefined; discarding old save_history=
/home/pocke/ghq/github.com/ruby/irb/lib/irb/extend-command.rb:239: warning: previous definition of save_history= was here
irb(main):001:0> 

This change will suppress the warnings.

Note

I cannot load irb/ext/tracer.rb because of an error.
So I don't touch the extension.

$ RUBYOPT='-w -Ilib/' exe/irb -f -r irb/ext/tracer
/home/pocke/ghq/github.com/ruby/irb/lib/irb/ext/tracer.rb:37: warning: method redefined; discarding old use_tracer=
/home/pocke/ghq/github.com/ruby/irb/lib/irb/extend-command.rb:239: warning: previous definition of use_tracer= was here
Traceback (most recent call last):
        12: from exe/irb:11:in `<main>'
        11: from /home/pocke/ghq/github.com/ruby/irb/lib/irb.rb:381:in `start'
        10: from /home/pocke/ghq/github.com/ruby/irb/lib/irb/init.rb:21:in `setup'
         9: from /home/pocke/ghq/github.com/ruby/irb/lib/irb/init.rb:281:in `load_modules'
         8: from /home/pocke/ghq/github.com/ruby/irb/lib/irb/init.rb:281:in `each'
         7: from /home/pocke/ghq/github.com/ruby/irb/lib/irb/init.rb:283:in `block in load_modules'
         6: from /home/pocke/.rbenv/versions/trunk/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:54:in `require'
         5: from /home/pocke/.rbenv/versions/trunk/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:54:in `require'
         4: from /home/pocke/ghq/github.com/ruby/irb/lib/irb/ext/tracer.rb:14:in `<top (required)>'
         3: from /home/pocke/ghq/github.com/ruby/irb/lib/irb/ext/tracer.rb:70:in `<module:IRB>'
         2: from /home/pocke/ghq/github.com/ruby/irb/lib/irb/ext/tracer.rb:19:in `initialize_tracer'
         1: from /home/pocke/.rbenv/versions/trunk/lib/ruby/2.7.0/tracer.rb:265:in `add_filter'
/home/pocke/.rbenv/versions/trunk/lib/ruby/2.7.0/tracer.rb:145:in `add_filter': wrong number of arguments (given 1, expected 0) (ArgumentError)

[aycabta]

It's a very important fix for tests, thank you!