added concrete IEqualityComparer<ExtensionIntPair> implementation in ExtensionRegistryLite.cs to prevent AOT compilation issue with unity in iOS
added concrete IEqualityComparer<ExtensionIntPair> implementation in ExtensionRegistryLite.cs to prevent AOT compilation issue with unity in iOS

Livefyre/protobuf,google/protobuf,google/protobuf,google/protobuf,Livefyre/protobuf,google/protobuf,Livefyre/protobuf,google/protobuf,Livefyre/protobuf,google/protobuf,google/protobuf,google/protobuf,Livefyre/protobuf,google/protobuf,google/protobuf,google/protobuf