Deprecate the old custom option

Makefile

@@ -21,8 +21,6 @@ GATEWAY_PLUGIN_SRC= protoc-gen-grpc-gateway/descriptor/name.go \
 		    protoc-gen-grpc-gateway/httprule/types_test.go \
 		    protoc-gen-grpc-gateway/main.go
 
-OLD_OPTIONS_PROTO=options/options.proto
-OLD_OPTIONS_GO=$(OLD_OPTIONS_PROTO:.proto=.pb.go)
 GOOGLEAPIS_DIR=third_party/googleapis
 OPTIONS_PROTO=$(GOOGLEAPIS_DIR)/google/api/annotations.proto $(GOOGLEAPIS_DIR)/google/api/http.proto
 OPTIONS_GO=$(OPTIONS_PROTO:.proto=.pb.go)
@@ -36,17 +34,14 @@ EXAMPLE_DEPS=examples/sub/message.proto
 EXAMPLE_DEPSRCS=$(EXAMPLE_DEPS:.proto=.pb.go)
 PROTOC_INC_PATH=$(dir $(shell which protoc))/../include
 
-generate: $(OPTIONS_GO) $(OLD_OPTIONS_GO)
+generate: $(OPTIONS_GO)
 
 .SUFFIXES: .go .proto
 
 $(GO_PLUGIN): 
 	go get $(GO_PLUGIN_PKG)
 	go build -o $@ $(GO_PLUGIN_PKG)
 
-$(OLD_OPTIONS_GO): $(OLD_OPTIONS_PROTO) $(GO_PLUGIN)
-	protoc -I $(PROTOC_INC_PATH)  -I. --plugin=$(GO_PLUGIN) --go_out=$(PKGMAP):. $(OLD_OPTIONS_PROTO)
-
 $(OPTIONS_GO): $(OPTIONS_PROTO) $(GO_PLUGIN)
 	protoc -I $(PROTOC_INC_PATH)  -I$(GOOGLEAPIS_DIR) --plugin=$(GO_PLUGIN) --go_out=$(PKGMAP):$(GOOGLEAPIS_DIR) $(OPTIONS_PROTO)
 
@@ -65,6 +60,6 @@ test: $(EXAMPLE_SVCSRCS) $(EXAMPLE_GWSRCS) $(EXAMPLE_DEPSRCS)
 
 clean distclean:
 realclean:
-	rm -f $(OLD_OPTIONS_GO) $(OPTIONS_GO)
+	rm -f $(OPTIONS_GO)
 	rm -f $(EXAMPLE_SVCSRCS) $(EXAMPLE_DEPSRCS)
 	rm -f $(EXAMPLE_GWSRCS)

options/options.proto

@@ -5,6 +5,9 @@ package gengo.grpc.gateway;
 import "google/protobuf/descriptor.proto";
 
 message ApiMethodOptions {
+	// Use HttpRule instead.
+	option deprecated = true;
+
 	extend google.protobuf.MethodOptions {
 		// Describes how the gRPC method should be exported as a RESTful API.
 		//