[Completion] Added conditional symbols to the completion engine

context.

ICSharpCode.NRefactory.CSharp/Completion/CSharpCompletionEngineBase.cs

@@ -682,6 +682,8 @@ namespace ICSharpCode.NRefactory.CSharp.Completion
 				wrapper.Append(new string('}', closingBrackets));
 			}
 			var parser = new CSharpParser ();
+			foreach (var sym in CompletionContextProvider.ConditionalSymbols)
+				parser.CompilerSettings.ConditionalSymbols.Add (sym);
 			parser.InitialLocation = new TextLocation(memberLocation.Line - generatedLines, 1);
 			var result = parser.Parse(wrapper.ToString ());
 			return result;

ICSharpCode.NRefactory.CSharp/Completion/ICompletionContextProvider.cs

@@ -35,6 +35,10 @@ namespace ICSharpCode.NRefactory.CSharp.Completion
 {
 	public interface ICompletionContextProvider
 	{
+		IList<string> ConditionalSymbols {
+			get;
+		}
+
 		void GetCurrentMembers (int offset, out IUnresolvedTypeDefinition currentType, out IUnresolvedMember currentMember);
 
 		Tuple<string, TextLocation> GetMemberTextToCaret(int caretOffset, IUnresolvedTypeDefinition currentType, IUnresolvedMember currentMember);
@@ -47,6 +51,12 @@ namespace ICSharpCode.NRefactory.CSharp.Completion
 		readonly IDocument document;
 		readonly CSharpUnresolvedFile unresolvedFile;
 
+		public IList<string> ConditionalSymbols {
+			get {
+				return new string[0];
+			}
+		}
+
 		public DefaultCompletionContextProvider (IDocument document, CSharpUnresolvedFile unresolvedFile)
 		{
 			if (document == null)

ICSharpCode.NRefactory.CSharp/Parser/CSharpParser.cs

@@ -3765,7 +3765,7 @@ namespace ICSharpCode.NRefactory.CSharp
 			}
 
 			conversionVisitor.Unit.FileName = fileName;
-			conversionVisitor.Unit.ConditionalSymbols = top.Conditionals.ToArray ();
+			conversionVisitor.Unit.ConditionalSymbols = top.Conditionals.Concat (compilerSettings.ConditionalSymbols).ToArray ();
 			return conversionVisitor.Unit;
 		}