Merge pull request #7475 from jcanizales/p0-advance-protobuf-version

.gitmodules

examples/cpp/helloworld/Makefile

examples/cpp/route_guide/Makefile

examples/objective-c/auth_sample/AuthTestService.podspec

examples/objective-c/helloworld/HelloWorld.podspec

examples/objective-c/route_guide/RouteGuide.podspec

gRPC-ProtoRPC.podspec

gRPC-RxLibrary.podspec

gRPC.podspec

include/grpc++/ext/reflection.pb.h

src/cpp/ext/reflection.pb.cc

src/objective-c/!ProtoCompiler-gRPCPlugin.podspec

src/objective-c/!ProtoCompiler.podspec

src/objective-c/README.md

src/objective-c/examples/RemoteTestClient/RemoteTest.podspec

src/objective-c/examples/SwiftSample/ViewController.swift

src/objective-c/tests/RemoteTestClient/RemoteTest.podspec

third_party/protobuf

tools/codegen/extensions/gen_reflection_proto.sh

tools/distrib/check_generated_pb_files.sh