Update server example to send to all clients.

[nemasu]

I changed the server example to send to all clients.

[dbcfd]

This should be another example, e.g. examples/broadcast_server. The existing example is meant to just echo a single connection.

[nemasu]

Ah okay, the description at the top says "A chat server that broadcasts a message to all connections."
I'll update that description for the existing example, and move this example to another file soon.