Fix compiler warnings
Fix ExpressionOfCompatibleTypeCastIssue.
Fix fixes an issue causing the type system to believe that accessors implement interface members even though there is an explicit implementation of the accessor owner.

Closes icsharpcode/NRefactory#170
NR.Demo: show details for Conversion objects
Merge branch 'extension-method-group-conversion' of github.com:erik-kallen/NRefactory
Rename IsExtensionMethodGroupConversion -> DelegateCapturesFirstArgument.
Fix NullReferenceException in SDWindowsFormsHost.GetInterface()
Merge changes from SharpDevelop repository to NRefactory.
Fix icsharpcode/NRefactory#181: default keyword doesn't resolve properly on enum types
Implemented GetAttributes() for members.
Fix icsharpcode/ILSpy#366
Disabled 'ParameterCanBeIEnumerableIssue'.
Fixed formatting bug.
Fixed abstract override in implement abstract members action.
Fixed bug in simplify anonymous method issue.
Improved type guessing logic.
Fixed formatting bug.
Make comment nodes for XML documentation part of the EntityDeclaration.

This removes the need for special cases in refactorings that move entities around.
Simplify code that checks whether an expression is a condition.
Updated mcs.