clang-format: Make braced list formatting more consistent.

Before:
  Aaaa aaaaaaaaaaa{
      {
       a, // +1 indent weird.
       b, // trailing comma signals one per line.
      },  // trailing comma signals one per line.
  };

After:
  Aaaa aaaaaaaaaaa{
      {
          a, // better!?
          b, // trailing comma signals one per line.
      },     // trailing comma signals one per line.
  };

Interesting that this apparently was entirely untested :-(.

llvm-svn: 230627