[clang-format] Put '/**' and '*/' on own lines in jsdocs ending in comment pragmas

Summary:
This handles a case where the trailing '*/' of a multiline jsdoc eding in a
comment pragma wouldn't be put on a new line.

Reviewers: mprobst

Reviewed By: mprobst

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D36359

llvm-svn: 310458