Add a very basic optimization pass

[fur] / examples / future / 34_except_finally.fur

def throws() do
  try
    42 // 0
  except(DivisionByZeroError)
    print('This should print first\n')
    42
  finally
    print('This should print second\n')
    1
  end
end

variable = throws()
print('This should print third\n')
print('This shoudld be 42: ', variable, '\n')