Merge pull request #381 from mono-soc-2013/MateY-IndentEngine

Issue with preprocessor directives.
Added 'CS1105ExtensionMethodMustBeDeclaredStaticAction'.
Fixed bug in 'XmlDocIssue'.
Formatting options change: blank lines are now >minimum< blank lines.
TODO: Add options for maximum blank lines to preserve.
Fixed bug in FunctionNeverReturnsIssue.
Handle errors if the XML file changes between the XmlDocumentationProvider ctor call and the GetDocumentation call.
Fix ICompilation.Import(ISymbol) for namespaces in extern alias.
Add IAstVisitor.VisitNullNode().
Fix #377 - NullReferenceException in NullAnalysisVisitor
Fix potential NullReferenceException in OperatorIsCanBeUsedIssue.
Merge NRefactory changes from SharpDevelop repository:

* TypeSystemAstBuilder: show async modifier only if ShowModifiers is set.
* remove wrong null-check in VariableReference implementation
* add ISymbolReference implementation
* fix icsharpcode/sharpdevelop#299: Declare local variable: Automatic variable naming
Fix bug in AstNode.GetNodesBetween().
Set XmlResolver=null to avoid looking up external DTDs.
Improved CS0618UsageOfObsoleteMemberIssue
Added failing unit test.
Try to use a syntactical approach for resolving lambda expressions.
Revert "Try to use a syntactical approach for resolving lambda expressions."

This reverts commit ffdb464e714c65265c9da90064e93cbc269e8c76.
Added another work around for the query variable issue.
Removed resolveinvocationongiventarget call.
Improved GetTypeForQueryVariable