UriParser.IsBaseOf now explicitly throws ArgumentNullException.
A change in Uri.Compare was making IsBaseOf to return false when arguments were null.
NullReferenceException is thrown by .NET, nonetheless the correct behavior is to throw a ArgumentNullException..
Merge pull request #1233 from esdrubal/uriparserisbaseof

UriParser.IsBaseOf now explicitly throws ArgumentNullException.