clang-format: Improve indentation of comments in expressions.

Before:
  int i = (a)
              // comment
          + b;
  return aaaa == bbbb
                 // comment
             ? aaaa
             : bbbb;
After:
  int i = (a)
          // comment
          + b;
  return aaaa == bbbb
             // comment
             ? aaaa
             : bbbb;

llvm-svn: 221985