merge with master, fix build issue

src/cpp/server/server_context.cc

tools/run_tests/tests.json

vsprojects/Grpc.mak

vsprojects/grpc.sln

vsprojects/grpc/grpc.vcxproj

vsprojects/grpc_cpp_plugin/grpc_cpp_plugin.vcxproj

vsprojects/grpc_csharp_ext/grpc_csharp_ext.vcxproj

vsprojects/grpc_csharp_plugin/grpc_csharp_plugin.vcxproj

...s/grpc_objective_c_plugin/grpc_objective_c_plugin.vcxproj

vsprojects/grpc_protoc_plugins.sln

vsprojects/grpc_python_plugin/grpc_python_plugin.vcxproj

vsprojects/grpc_ruby_plugin/grpc_ruby_plugin.vcxproj

vsprojects/grpc_unsecure/grpc_unsecure.vcxproj