HDFS-9497. move lib/proto/cpp_helpers to third-party since it won't have an ASF license. Contributed by Bob Hansen.

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/CMakeLists.txt

@@ -52,6 +52,7 @@ include_directories(
   third_party/rapidxml-1.13
   third_party/gmock-1.7.0
   third_party/tr2
+  third_party/protobuf
   ${OPENSSL_INCLUDE_DIR}
   ../libhdfs/include
 )

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/lib/proto/protoc_gen_hrpc.cc

@@ -16,7 +16,7 @@
  * limitations under the License.
  */
 
-#include "cpp_helpers.h"
+#include "protobuf/cpp_helpers.h"
 
 #include <google/protobuf/compiler/code_generator.h>
 #include <google/protobuf/compiler/plugin.h>