Fix a few oversights in the clang-tidy VS plugin.

Over-zealous cleanup of using statements removed some that were
actually needed.  Also cleaned up a few warnings.

llvm-svn: 280844

clang-tools-extra/clang-tidy-vs/ClangTidy/CheckDatabase.cs

@@ -50,7 +50,7 @@ namespace LLVM.ClangTidy
                 foreach (var Check in Checks_)
                 {
                     if (Names.Contains(Check.Name))
-                        throw new ArgumentException(String.Format("Check {0} exists more than once!", Check.Name));
+                        continue;
                     Names.Add(Check.Name);
                 }
             }

clang-tools-extra/clang-tidy-vs/ClangTidy/CheckTree.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Linq;
 using System.Text;
 
 namespace LLVM.ClangTidy

clang-tools-extra/clang-tidy-vs/ClangTidy/ClangTidyProperties.cs

@@ -40,7 +40,6 @@ namespace LLVM.ClangTidy
         static ClangTidyProperties()
         {
             RootProperties_ = new ClangTidyProperties(null);
-            PropertyDescriptor D;
         }
 
         public static ClangTidyProperties RootProperties

clang-tools-extra/clang-tidy-vs/ClangTidy/ClangTidyPropertyGrid.cs

@@ -42,13 +42,6 @@ namespace LLVM.ClangTidy
         /// </summary>
         List<KeyValuePair<string, ClangTidyProperties>> PropertyChain_ = null;
 
-        /// <summary>
-        /// A tree representing all the checks that the extension knows about, used
-        /// when serializing a file to intelligently determine when to use wildcard
-        /// include / exclude rules.
-        /// </summary>
-        CheckTree Checks_;
-
         public ClangTidyPropertyGrid()
         {
             InitializeComponent();