install_extend_commands

Installs the default context extensions as irb commands:

IRB::Context#eval_history=

irb/ext/history.rb

IRB::Context#use_tracer=

irb/ext/tracer.rb

IRB::Context#math_mode=

irb/ext/math-mode.rb

IRB::Context#use_loader=

irb/ext/use-loader.rb

IRB::Context#save_history=

irb/ext/save-history.rb