MINOR: hlua: Add support for lua 5.5

MINOR: hlua: Add support for lua 5.5

Lua 5.5 adds an extra argument to lua_newstate(). Since there are
already a few other ifdefs in hlua.c checking for the Lua version,
and there's a single call place, let's do the same here. This should
be safe for backporting if needed.

Signed-off-by: Mike Lothian <mike@fireburn.co.uk>