twister-core 0.9.31: security fixes and more

Hi,

I’ve finally backported two security fixes from libtorrent: uTP vulnerability (also known as DRDoS in torrent world) and lazy_bdecode overrun.

These are already in github tagged with version 0.9.31.

Also notice that recent changes in twister-core are also required to enable the new twister-html features:

- RT with comments and
- Group Chat!

Thanks a lot @tasty and @erkanyuksel for their work!