A script "[print(1)]; print(2)" should output "12".
  However, the compiler had eliminted "[print(1)]" expression
  because it is void expression (unused array).
  Of course, side-effect should be remained.
  This issue is reported by Masaya Tarui.
* bootstraptest/test_literal.rb: add a test.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38751 b2dd03c8-39d4-4d8f-98ff-823fe69b080e