PRs from postgres-ast-deparser for reference

[pyramation]

these should eventually be included in this library to have feature parity:

• [ ] https://github.com/pyramation/postgres-ast-deparser/pull/11
• [ ] https://github.com/pyramation/postgres-ast-deparser/pull/10
• [ ] https://github.com/pyramation/postgres-ast-deparser/pull/9
• [ ] https://github.com/pyramation/postgres-ast-deparser/pull/6
• [ ] https://github.com/pyramation/postgres-ast-deparser/pull/4