clang-format: Increase penalty for wrapping array subscript expressions

Before:
  aaaaaaaaaaa aaaaaaaaaaaaaaa = aaaaaaaaaaaaaaaaaaaaaaaaaa->aaaaaaaaa[0].aaaaaaa
                                    [0].aaaaaaaaaaaaaaaaaaaaaa();

After:
  aaaaaaaaaaa aaaaaaaaaaaaaaa = aaaaaaaaaaaaaaaaaaaaaaaaaa->aaaaaaaaa[0]
                                    .aaaaaaa[0]
                                    .aaaaaaaaaaaaaaaaaaaaaa();

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@210529 91177308-0d34-0410-b5e6-96231b3b80d8