@link tag support

should suport:

```
{@link someSymbol}
{@link http://some.url.com}
[caption here]{@link someSymbol}
[caption here]{@link http://some.url.com}
{@link someSymbol|caption here}
{@link http://some.url.com|caption here}
{@link http://some.url.com Caption Here (after the first space)}
{@link someSymbol Caption Here (after the first space)}
```

and `@linkplain` and `@linkcode` tags.