Solidity Natspec multiline /** .. */ comments

- Natspec now works with `/** ... */` type of comments.
- Some work on better formatting of the extracted text, especially on the multiline comments case
- Adding CR ('\r') as whitespace in the scanner
- Some tests
It all depends on a case by case basis. Introducing extra check on something that's used frequently in favour of readability does not sound good to me. But this paritcular function is (at the moment) only used at one place so it can be.