Merge pull request grpc#8543 from apolcyn/fix_ruby_plugin_build

fix type comparison in ruby plugin

Merge pull request grpc#8480 from muxi/finalize-release-v1.0.1-pre1

Protobuf versioning in v1.0.1-pre1

Merge pull request grpc#7787 from nicolasnoble/quick-fix-for-manylinux

Disabling check for SO_REUSEPORT in MANYLINUX; it'll always fail.

Merge pull request grpc#7717 from nicolasnoble/update-build-packages

Updating build package C# scripts.

Merge pull request grpc#7388 from stanley-cheung/php-fix-interop-test…

…-0_15

PHP: fix interop tests breakage

0.15.1 Release

Merge pull request grpc#7064 from jtattermusch/fix_ruby_package_build

fix building ruby package