Ruby 2.0 parser doesn't intern symbol strings in literal symbol array

Symbols created using a literal symbol array don't have the same identities as the same symbols created outside of a literal symbol array:

```
$ JRUBY_OPTS="--2.0" jirb
2.0.0-p247 :001 > [JRUBY_VERSION, RUBY_VERSION]
 => ["1.7.5.dev", "2.0.0"]
2.0.0-p247 :002 > %i(foo).include?(:foo)
 => false
```

org.jruby.parser.ParserSupport#asSymbol is not interning. This pull request adds the intern() call.