IRB v2.0

[st0012]

This is the meta issue for collecting breaking changes we're going to make in IRB v2.0

• RubyLex: Remove deprecated toplevel ::RubyLex #1155
• Multi-irb commands: Deprecate multi-irb feature #653
• LOAD_MODULES feature
• USE_RELINE and USE_REIDLINE en vars
• IRB::Context#prompt_n[=] methods
• ExtendCommandBundle

[tompng]

I want to remove use of extract_ruby_args before v2.0.
It's used in measure, irb_load, irb_require, irb_source command.
Example: reject measure ("o"+"n").to_sym and only accept something like measure :on or measure on