Just send a pull request. First time in my life 
Please, let me know if any additional information should be provided or any modification to the code must be done.
I had created gradle subproject named 'hoxt' (abbreviation of "Http Over Xmpp Transport").
I had also added this subproject into smack's settings.gradle.
Beside that the code is really trivial. There are no android/java se specific features. So, I expect no problems on those platforms.
The code also re-uses code for shim extension.
The only limitation is that 2 featres of xep-0332 are not supported: jingle and sipub. They are not used yet