Print like types

Print like types

Summary: This adds printing of like types for the locl ty case (union with dynamic), while the decl ty case is handled by `Tlike`. Following the existing implementation of complex unions with null, I went with `~` in front instead of union with `dynamic`, i.e. `(dynamic | null | int | string)` prints as `~?(int | string)` instead of `?(dynamic | int | string)`.

Reviewed By: dlreeves

Differential Revision: D15349710

fbshipit-source-id: 8ddef46e58c16b4a4ae8fc69a29f1fdaf18f8ba9