[Screeninvader] Lua execution blocks execution

[phaer]

Hi,

It looks like the Janosh process gets still blocked while
lua scripts are executing. It's easily reproducable by
running ~lounge/socket-server-test.lua and trying to run
another janosh command or access the screeninvader gui at
the same time.

I am neither familiar with Janosh internals nor with boosts
threading capabilities, so I thought I just report it here.