Tests and fixes for double-enumeration on AddRange and adding of null to PopsicleList
diff --git a/src/ProtocolBuffers.Test/TestProtos/UnitTestEmbedOptimizeForProtoFile.cs b/src/ProtocolBuffers.Test/TestProtos/UnitTestEmbedOptimizeForProtoFile.cs
index 09ecdd6..a15488c 100644
--- a/src/ProtocolBuffers.Test/TestProtos/UnitTestEmbedOptimizeForProtoFile.cs
+++ b/src/ProtocolBuffers.Test/TestProtos/UnitTestEmbedOptimizeForProtoFile.cs
@@ -246,7 +246,7 @@
           MergeOptionalMessage(other.OptionalMessage);

         }

         if (other.repeatedMessage_.Count != 0) {

-          base.AddRange(other.repeatedMessage_, result.repeatedMessage_);

+          result.repeatedMessage_.Add(other.repeatedMessage_);

         }

         this.MergeUnknownFields(other.UnknownFields);

         return this;

@@ -379,7 +379,7 @@
         return this;

       }

       public Builder AddRangeRepeatedMessage(scg::IEnumerable<global::Google.ProtocolBuffers.TestProtos.TestOptimizedForSize> values) {

-        base.AddRange(values, result.repeatedMessage_);

+        result.repeatedMessage_.Add(values);

         return this;

       }

       public Builder ClearRepeatedMessage() {