ecma_transforms:
- implement es2015::instanceof
- implement es2015::typeof_symbol
- implement inline_globals pass
ecma_parser:
- `PResult<T>` is now `Result<T, ()>` and `Err(())` means that an error is emitted.
- add docs
- Parser and lexer for lastest ecma spec https://tc39.github.io/ecma262
- Lexer is currently very inefficient
- Use https://github.com/tc39/test262-parser-tests/ for testing.
- Implement proc-macro based ast folder and assert_eq_ignore_span! based on it.
- Some utilities for proc macro at /macros/common
