ClangFormat: no way to prevent alignment of streaming operators/operator<<

As described in https://stackoverflow.com/questions/38699555/clang-format-stream-output, there's no way to have e.g. 4 spaces of indentation to align streaming operators:

```
std::cout << 1 << 1 << 1 << 1 << 1 << 1 <<
    1 << 1 << 1 << 1 << 1 << 1;
```

because it always gets aligned to the previous line:
```
std::cout << 1 << 1 << 1 << 1 << 1 << 1
          << 1 << 1 << 1 << 1 << 1 << 1;
```
