clang-format: Fix formatting of nested blocks after comment.

Before:
  DEBUG({ // Comment that used to confuse clang-format.
  fdafas();
  });
Before:
  DEBUG({ // Comments are now fine.
    fdafas();
  });

This fixed llvm.org/PR17619.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193051 91177308-0d34-0410-b5e6-96231b3b80d8