select for Linux needs the nfds parameter set correctly

Finally got the Debian 7 working and tested "Websockets for Lua" in Linux.
In contrast to Windows, Linux uses the first param in select.

With this fix, the "Websocket for Lua" example works for Linux:
1) build WITH_LUA and WITH_WEBSOCKET
2) set document_root to the test/ directory and listening_port to 80
3) open websocket.xhtml and watch the server clock