Print error before cleanup in codegen_error()

[dearblue]

Previously, it always pointed to the highest scope as the location of the error.

• example code code.rb

  huge_num = "1" + "0" * 300; eval <<CODE, nil, "test.rb", 1
  class Object
    module A
      #{huge_num}
    end
  end
  CODE

• Before this patch

  % bin/mruby code.rb
  test.rb:1: integer too big
  trace (most recent call last):
          [1] code.rb:1
  code.rb:1:in eval: codegen error (ScriptError)

• After this patch

  % bin/mruby code.rb
  test.rb:3: integer too big
  trace (most recent call last):
          [1] code.rb:1
  code.rb:1:in eval: codegen error (ScriptError)