- Use poll() instead of select to allow breaking the FD_SETSIZE barrier

- Use poll() instead of select to allow breaking the FD_SETSIZE barrier
- Poll the system clock only once per loop (yes, it DOES matter),
- Fix rare bug with TLS and multiple listening sockets,
- Do not try to read/write to client socket with no pending events.
...and of course introduce dozens of new bugs.

This SHOULD speed httpd up a bit.