Fixed bug in CreateEnumValue/improved type guessing.
Suppress OptionalParameterHierarchyMismatchIssue in explicit interface implementations.
Remove the upcast in InheritanceHelper.GetBaseMembers()
Merge NRefactory changes from the SharpDevelop repository.

Includes Siegfried's work on the output visitor (ITokenWriter) and some minor bugfixes.
Add back CSharpOutputVisitor.ConvertString().
Fixed bug in format method recognition.
Fixed bug in ConvertToStaticTypeIssue
Fixed potential null reference exception in the c# parser.
Failing test for https://bugzilla.xamarin.com/show_bug.cgi?id=16997
Fixed some issues in redundant unsafe context issue
Fixed bug invoking inherited methods (eg. ToString()) on anonymous types
Added test for the parser null ref exception.
Fixed bug in SegmentTrackingTokenWriter.
Improved lambda parameter recognition.
Fixed a wrapping bug.
Fixed formatting bug.
Fixed formatting bug.
Added failing method continuation test.
TestMethodContinuationCase3
Issue with continuation delta.

When replacing ThisLineIndent with NextLineIndent, only one indentation
delta (and only if it's a continuation) is allowed.