Merge branch 'master' of https://github.com/grpc/grpc into include-new-ruby-interop-tests

src/core/ext/client_channel/http_connect_handshaker.c

src/core/ext/client_channel/http_connect_handshaker.h

src/ruby/pb/test/client.rb

templates/tools/doxygen/Doxyfile.include

test/http2_test/http2_base_server.py

test/http2_test/http2_test_server.py

tools/doxygen/Doxyfile.c++

tools/doxygen/Doxyfile.c++.internal

tools/doxygen/Doxyfile.core

tools/doxygen/Doxyfile.core.internal