Mark j2objc proto "new" functions as returning retained values. This
prevents leaks of builders and their associated messages when the generated
proto classes use these functions when compiled under ARC.
CF_EXTERN_C_BEGIN
-ComGoogleProtobufGeneratedMessage *CGPNewMessage(
+NS_RETURNS_RETAINED ComGoogleProtobufGeneratedMessage *CGPNewMessage(
ComGoogleProtobufDescriptors_Descriptor *descriptor);
-ComGoogleProtobufGeneratedMessage_Builder *CGPNewBuilder(
+NS_RETURNS_RETAINED ComGoogleProtobufGeneratedMessage_Builder *CGPNewBuilder(
ComGoogleProtobufDescriptors_Descriptor *descriptor);
ComGoogleProtobufGeneratedMessage_Builder *CGPBuilderFromPrototype(
