Fix most common parsing failures when @ is present in the docblock but not for an annotation

Replaces https://github.com/doctrine/common/pull/195  - in the most common path this just adds one `in_array($input[$pos], array(' ', '*', '@', '/'))` call which I think is worth fixing this WTF-inducing-bug, really not much compared to the whole annotation parsing, and it's cached anyway right?