test/ruby/test_optimization.rb (test_hash_aset_with): assert assignment

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47920 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test/ruby/test_optimization.rb: redefinition tests for String

* test/ruby/test_optimization.rb (test_string_eq_neq): new test
  (test_string_ltlt): ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47921 b2dd03c8-39d4-4d8f-98ff-823fe69b080e