Install clang-format's editor integrations in $PREFIX/share/clang/

They were previously not part of the install target.

Differential Revision: http://llvm-reviews.chandlerc.com/D2154

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194741 91177308-0d34-0410-b5e6-96231b3b80d8