Update //third_party/protobuf to version 3.

third_party/protobuf/cmake/protobuf-module.cmake.in

+if(PROTOBUF_SRC_ROOT_FOLDER)
+  message(AUTHOR_WARNING "Variable PROTOBUF_SRC_ROOT_FOLDER defined, but not"
+    " used in CONFIG mode")
+endif()
+
+function(PROTOBUF_GENERATE_CPP SRCS HDRS)
+  if(NOT ARGN)
+    message(SEND_ERROR "Error: PROTOBUF_GENERATE_CPP() called without any proto files")
+    return()
+  endif()
+
+  if(PROTOBUF_GENERATE_CPP_APPEND_PATH)
+    # Create an include path for each file specified
+    foreach(FIL ${ARGN})
+      get_filename_component(ABS_FIL ${FIL} ABSOLUTE)
+      get_filename_component(ABS_PATH ${ABS_FIL} PATH)
+      list(FIND _protobuf_include_path ${ABS_PATH} _contains_already)
+      if(${_contains_already} EQUAL -1)
+          list(APPEND _protobuf_include_path -I ${ABS_PATH})
+      endif()
+    endforeach()
+  else()
+    set(_protobuf_include_path -I ${CMAKE_CURRENT_SOURCE_DIR})
+  endif()
+
+  # Add well-known type protos include path
+  list(APPEND _protobuf_include_path
+    -I "${_PROTOBUF_IMPORT_PREFIX}/@CMAKE_INSTALL_INCLUDEDIR@")
+
+  if(DEFINED PROTOBUF_IMPORT_DIRS)
+    foreach(DIR ${PROTOBUF_IMPORT_DIRS})
+      get_filename_component(ABS_PATH ${DIR} ABSOLUTE)
+      list(FIND _protobuf_include_path ${ABS_PATH} _contains_already)
+      if(${_contains_already} EQUAL -1)
+          list(APPEND _protobuf_include_path -I ${ABS_PATH})
+      endif()
+    endforeach()
+  endif()
+
+  set(${SRCS})
+  set(${HDRS})
+  foreach(FIL ${ARGN})
+    get_filename_component(ABS_FIL ${FIL} ABSOLUTE)
+    get_filename_component(FIL_WE ${FIL} NAME_WE)
+
+    list(APPEND ${SRCS} "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.pb.cc")
+    list(APPEND ${HDRS} "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.pb.h")
+
+    add_custom_command(
+      OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.pb.cc"
+             "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.pb.h"
+      COMMAND ${PROTOBUF_PROTOC_EXECUTABLE}
+      ARGS --cpp_out  ${CMAKE_CURRENT_BINARY_DIR} ${_protobuf_include_path} ${ABS_FIL}
+      DEPENDS ${ABS_FIL} ${PROTOBUF_PROTOC_EXECUTABLE}
+      COMMENT "Running C++ protocol buffer compiler on ${FIL}"
+      VERBATIM)
+  endforeach()
+
+  set_source_files_properties(${${SRCS}} ${${HDRS}} PROPERTIES GENERATED TRUE)
+  set(${SRCS} ${${SRCS}} PARENT_SCOPE)
+  set(${HDRS} ${${HDRS}} PARENT_SCOPE)
+endfunction()
+
+# Internal function: search for normal library as well as a debug one
+#    if the debug one is specified also include debug/optimized keywords
+#    in *_LIBRARIES variable
+function(_protobuf_find_libraries name filename)
+   get_target_property(${name}_LIBRARY lib${filename}
+     IMPORTED_LOCATION_RELEASE)
+   set(${name}_LIBRARY "${${name}_LIBRARY}" PARENT_SCOPE)
+   get_target_property(${name}_LIBRARY_DEBUG lib${filename}
+     IMPORTED_LOCATION_DEBUG)
+   set(${name}_LIBRARY_DEBUG "${${name}_LIBRARY_DEBUG}" PARENT_SCOPE)
+
+   if(NOT ${name}_LIBRARY_DEBUG)
+      # There is no debug library
+      set(${name}_LIBRARY_DEBUG ${${name}_LIBRARY} PARENT_SCOPE)
+      set(${name}_LIBRARIES     ${${name}_LIBRARY} PARENT_SCOPE)
+   else()
+      # There IS a debug library
+      set(${name}_LIBRARIES
+          optimized ${${name}_LIBRARY}
+          debug     ${${name}_LIBRARY_DEBUG}
+          PARENT_SCOPE
+      )
+   endif()
+endfunction()
+
+# Internal function: find threads library
+function(_protobuf_find_threads)
+    set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
+    find_package(Threads)
+    if(Threads_FOUND)
+        list(APPEND PROTOBUF_LIBRARIES ${CMAKE_THREAD_LIBS_INIT})
+        set(PROTOBUF_LIBRARIES "${PROTOBUF_LIBRARIES}" PARENT_SCOPE)
+    endif()
+endfunction()
+
+#
+# Main.
+#
+
+# By default have PROTOBUF_GENERATE_CPP macro pass -I to protoc
+# for each directory where a proto file is referenced.
+if(NOT DEFINED PROTOBUF_GENERATE_CPP_APPEND_PATH)
+  set(PROTOBUF_GENERATE_CPP_APPEND_PATH TRUE)
+endif()
+
+# The Protobuf library
+_protobuf_find_libraries(PROTOBUF protobuf)
+
+# The Protobuf Lite library
+_protobuf_find_libraries(PROTOBUF_LITE protobuf-lite)
+
+# The Protobuf Protoc Library
+_protobuf_find_libraries(PROTOBUF_PROTOC protoc)
+
+if(UNIX)
+  _protobuf_find_threads()
+endif()
+
+# Set the include directory
+set(PROTOBUF_INCLUDE_DIR "${_PROTOBUF_IMPORT_PREFIX}/@CMAKE_INSTALL_INCLUDEDIR@")
+
+# Set the protoc Executable
+get_target_property(PROTOBUF_PROTOC_EXECUTABLE protoc
+  IMPORTED_LOCATION_RELEASE)
+if(NOT PROTOBUF_PROTOC_EXECUTABLE)
+  get_target_property(PROTOBUF_PROTOC_EXECUTABLE protoc
+    IMPORTED_LOCATION_DEBUG)
+endif()
+
+include(FindPackageHandleStandardArgs)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(PROTOBUF DEFAULT_MSG
+    PROTOBUF_LIBRARY PROTOBUF_INCLUDE_DIR)
+
+if(PROTOBUF_FOUND)
+    set(PROTOBUF_INCLUDE_DIRS ${PROTOBUF_INCLUDE_DIR})
+endif()