* Allow type predicates
1. Parse type predicates. Note that they are parsed everywhere, and get
the appropriate error when used places besides a return type.
2. When creating a type predicate, correctly find the function's parameters
starting from the jsdoc return type.
* Fix type of TypePredicateNode.parent: add JSDocTypeExpression
* Update API baselines
* Handle JSDoc signature inside @type annotations
* Fix circularity when getting type predicates
Also move createTypePredicateFromTypePredicateNode closer to its use
* More cleanup based on review comments
