Consider setting `SEARCHENGINE = YES` in doc/Doxyfile.in#L1214

[Lars]

Hi,

there is no search box in the libnl Documentation at

https://www.infradead.org/~tgr/libnl/doc/api/index.html


As far as I understand this could be fixed by setting

```
SEARCHENGINE = YES
```

in

https://github.com/tgraf/libnl/blob/43bfe43fc58130efa3bda010621aef67a279faca/doc/Doxyfile.in#L1214

Is there any reason why it is set to NO?

Best regards,
Lars