[Bug #21394]

There are two ways to make RubyVM::InstructionSequence.new raise which
would cause the options->scopes to leak memory:

1. Passing in any (non T_FILE) object where the to_str raises.
2. Passing in a T_FILE object where String#initialize_dup raises. This is
   because rb_io_path dups the string.

Example 1:

    10.times do
      100_000.times do
        RubyVM::InstructionSequence.new(nil)
      rescue TypeError
      end

      puts `ps -o rss= -p #{$$}`
    end

Before:

    13392
    17104
    20256
    23920
    27264
    30432
    33584
    36752
    40032
    43232

After:

    9392
    11072
    11648
    11648
    11648
    11712
    11712
    11712
    11744
    11744

Example 2:

    require "tempfile"

    MyError = Class.new(StandardError)
    String.prepend(Module.new do
      def initialize_dup(_)
        if $raise_on_dup
          raise MyError
        else
          super
        end
      end
    end)

    Tempfile.create do |f|
      10.times do
        100_000.times do
          $raise_on_dup = true
          RubyVM::InstructionSequence.new(f)
        rescue MyError
        else
          raise "MyError was not raised during RubyVM::InstructionSequence.new"
        end

        puts `ps -o rss= -p #{$$}`
      ensure
        $raise_on_dup = false
      end
    end

Before:

    14080
    18512
    22000
    25184
    28320
    31600
    34736
    37904
    41088
    44256

After:

    12016
    12464
    12880
    12880
    12880
    12912
    12912
    12912
    12912
    12912