Format output closer to what clang-format would output

[timwoj]

While working directly on a pac.cc file generated from a large analyzer, my Emacs session reformatted the whole file based on the clang-format configuration used by all of the Zeek projects. This took a very long time, since the change set was pretty large. This PR changes the output from binpac to be much closer to what clang-format would output. It's not perfect, since clang-format will do things like compressing empty blocks or splitting long lines, and we can't do that easily in binpac.

[ckreibich]

Thank you!

[ckreibich]

No biggie but this can apparently still leave empty pairs of curly braces, like this example from Zeek's websocket_pac.cc:

WebSocket_FrameHeader::~WebSocket_FrameHeader() {
    switch ( maybe_more_len_case_index() ) {
        case ((uint8)126):
            // Clean up "payload_len2"
            {
            }
            break;
        case ((uint8)127):
            // Clean up "payload_len8"
            {
            }
            break;
        default:
            // Clean up "short_len"
            {
            }
            break;
    }

Just in case you want to iterate on that one.

[timwoj]

We shouldn't even generate those case blocks if they're not doing anything. Unfortunately we can't know they're not going to be blank until we call GenCleanUpCode on the object, which does it's own output to the file. There's a lot of places in binpac where that kind of thing happens.

In this case though, I can't squash those because the check there is for an anonymous field. These cleanup blocks are for named fields in binpac, and it has to call GenCleanUpCode on them even if it's going to return nothing.