util.strbitop: Add common_prefix_bits() method
This returns the number of bits that two strings have in common. It is
significantly more efficient than similar calculations in Lua.
For full information on our dependencies, version requirements, and
where to find them, see https://prosody.im/doc/depends
If you have luarocks available on your platform, install the following:
- luaexpat
- luasocket
- luafilesystem
- luasec