[clang-format] Keep protobuf "package" statement on one line

Summary:
Top-level "package" and "import" statements should generally be kept on one
line, for all languages.

Reviewers: sammccall, krasimir, MyDeveloperDay

Reviewed By: MyDeveloperDay

Subscribers: MyDeveloperDay, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D59627

Patch By: dchai (Donald Chai)

llvm-svn: 356835