Add backwards compatibility wrappers for socket.unix
Add backwards compatibility wrappers for socket.unix

Add backwards compatibility aliases "tcp" and "udp" for the recently renamed
"stream" and "dgram" functions, as well as a wrapper function and metatable
setup so that socket.unix() calls socket.unix.stream().

diegonehab/LuaSocket,cjtallman/luasocket,cjtallman/luasocket,cjtallman/luasocket,cjtallman/luasocket,diegonehab/LuaSocket,diegonehab/LuaSocket