doc: add precision about -buffer switch on eval/exec

Relevant filter in the code:
```
        if (*bufnames == "*")
        {
            for (auto&& buffer : BufferManager::instance()
                               | transform(&std::unique_ptr<Buffer>::get)
                               | filter([](Buffer* buf) { return not (buf->flags() & Buffer::Flags::Debug); })
                               | gather<Vector<SafePtr<Buffer>>>()) // gather as we might be mutating the buffer list in the loop.
                context_wrap_for_buffer(*buffer);
        }

```

0 files changed, 0 insertions, 0 deletions