Decorator Syntax Errors

So decorators have very strict syntax, while in reality, any valid python expression can be used when decorating. See github's highlighting below too.

* **Editor name and version**: Sublime Text 4152
* **Platform**: MacOSX
* **Color scheme**: Custom, but any
* **MagicPython version**: v.1.1.1
* **A sreenshot**:
* 
* **5-10 lines of surrounding code**:
```python
class A:
@D[C][prtl]
def a(self):
pass

@a | b | c
def a(self):
pass
```

Start by reproducing the two decorator examples in Sublime Text with MagicPython v1.1.1 and compare their highlighting with GitHub's result. Then locate the decorator syntax-highlighting entry point in the repository and identify the existing tests for decorators, if any. Done means both valid expressions are highlighted as decorators without syntax errors.

Written by the indexing model from the issue text.