Pass __FILE__ and __LINE__ into URIException

`__FILE__` and `__LINE__` were not properly passed into URIException. However
passing them as arguments makes it ambigous. Therefore remove the unused
empty constructor.

The other option is to not remove it but pass it as a template parameter, e.g.:
```D
this(string fn == __FILE__, size_t ln = __LINE__)(string msg)
```