Code Review: gsub_classdup

tfpt review /shelveset:gsub_classdup;REDMOND\tomat

Fixes bug #20199: Getting metaclass for nil causes a .NET exception
Fixes bug #20137: gsub $n bug
Fixes bug #19902: Regex global matching vars are not nil when they don’t
match
Fixes bug #20222: super call in initialize method of a module
Fixes bug #20011: Can’t subclass module

  •   Also implements Module#initialize, Module#initialize_copy.
    

Reviewed F2F by John.

Tomas