I am no longer working on this, primarily because I stopped watching TV and thus using tvheadend. Also, if you export an m3u playlist of your channels from tvh, and open it in VLC, you have the same set of features this plugin offers, just without all the weird bugs.
Compile using make and put resulting libhtsp_plugin.so somewhere VLC finds it.
Some settings are available for the service discovery. Filter advanced settings for HTS to easily find them.
URL format is htsp://{username{:password}@}server{:port}/channelId
The Service Discovery module is listed under LAN and grabs the channel list from TVH.