Merge pull request #3065 from yang-g/string_ref

Makefile

build.json

include/grpc++/client_context.h

include/grpc++/impl/call.h

include/grpc++/server_context.h

include/grpc++/support/string_ref.h

src/cpp/common/call.cc

src/cpp/server/server.cc

src/cpp/server/server_context.cc

src/cpp/util/string_ref.cc

test/cpp/end2end/async_end2end_test.cc

test/cpp/end2end/end2end_test.cc

test/cpp/util/cli_call.cc

test/cpp/util/cli_call.h

test/cpp/util/cli_call_test.cc

test/cpp/util/grpc_cli.cc

test/cpp/util/string_ref_helper.cc

test/cpp/util/string_ref_helper.h

tools/run_tests/sources_and_headers.json

vsprojects/Grpc.mak