Merge branch 'master' of https://github.com/grpc/grpc into interop_server_split

Makefile

build.yaml

examples/php/composer.json

package.xml

setup.py

...ore/ext/transport/chttp2/client/insecure/channel_create.c

...xt/transport/chttp2/client/secure/secure_channel_create.c

...core/ext/transport/chttp2/server/insecure/server_chttp2.c

...ext/transport/chttp2/server/secure/server_secure_chttp2.c

src/core/lib/channel/handshaker.c

src/core/lib/channel/handshaker.h

src/core/lib/security/transport/handshake.c

src/core/lib/transport/transport.h

src/csharp/Grpc.Core/GrpcEnvironment.cs

...objective-c/tests/InteropTestsRemoteWithCronet/Info.plist

...teropTestsRemoteWithCronet/InteropTestsRemoteWithCronet.m

src/objective-c/tests/Podfile

src/objective-c/tests/Tests.xcodeproj/project.pbxproj

...hareddata/xcschemes/InteropTestsRemoteWithCronet.xcscheme

src/php/README.md