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

Revert "Revert "[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.

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This reverts commit rL356912.
The regression from rL356835 was fixed via rC358275.

Reviewers: krasimir, sammccall, MyDeveloperDay, xinz, dchai, klimek

Reviewed By: krasimir, xinz, dchai

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D60661

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@360411 91177308-0d34-0410-b5e6-96231b3b80d8