Update to NRefactory commit '2a46efacdad982a6fcf07303f57a917585356462'

2a46efa CSharpResolver: return ErrorResolveResult instead of crashing when given an invalid operator type.
2371920 Merge pull request icsharpcode/NRefactory#388 from mono-soc-2013/MateY-IndentEngine
dec33c5 Fixed Bug 18463
9719b41 Added failing unit test.
9d2209e Updated mcs
98f042d Fix icsharpcode/SharpDevelop#404: Crash in CSharpCompletionEngine.GetLineIndent() when line has no indentation.
39e17c9 Documentation for IAmbience
01bf167 Fix icsharpcode/NRefactory#386: A using statement referring to a missing nested type causes infinite recursion in resolver
2cd1a17 Re-enable NameLookupTests.NamespaceDefinitionOverwritesTypeName
0c4a81e Fixed bug in using declaration namespace name.
09531ca Fixed bug in in IndentBlocksInsideExpressions option.
484160b Added 'IndentBlocksInsideExpressions' formatting option.
a35eafb Improved event method naming.
fd9e073 Removed duplicate event creation data.
81436d0 Added new 'bold' display flag for code completion.