[IR] Fixed some missing nonlocal-return handling support.

* Existing support for nonlocal return was missing support
  for nonlocal returns origination in evals. See two snippets
  below. This commit fixes that.

    def bar; yield; end
    def foo
      bar { eval "return 2" }
    end

    p foo
    p lambda { eval("return :eval") }.call

* This eliminates 1 error and 1 failure from Kernel#eval runspecs.
  Now down to 9 failures and 2 errors.