Fixes a trio of concurrency issues found by Coverity

Author: J Wyman

LibGit2Sharp/Core/Handles/SafeHandleBase.cs

@@ -66,7 +66,15 @@ public static void Clear()
         /// </summary>
         public static IEnumerable<string> TypeNames
         {
-            get { return _typeNames.ToArray(); }
+            get
+            {
+                string[] result = null;
+                lock (_lockpad)
+                {
+                    result = _typeNames.ToArray();
+                }
+                return result;
+            }
         }
     }
 }

LibGit2Sharp/Core/LazyGroup.cs

@@ -24,18 +24,19 @@ public ILazy<TResult> AddLazy<TResult>(Func<T, TResult> func)
 
         public void Evaluate()
         {
-            if (evaluated)
-                return;
-
             lock (@lock)
             {
                 if (evaluated)
+                {
                     return;
+                }
 
                 EvaluateInternal(input =>
                                  {
                                      foreach (var e in evaluators)
+                                     {
                                          e.Evaluate(input);
+                                     }
                                  });
                 evaluated = true;
             }