Currently, in sock_read_write function, if the timeout is 0, pupnp
realizes a "blocking" select (with an infinite timeout). With this
patch, if timeout is set to 0, pupnp will realize a "polling" select
and returns immediately if it can not read or write on the socket. This
is very useful for GENA notifications when pupnp is trying to send
events to a disconnected Control Point. "Blocking" select can now be
done by putting a negative timeout value.
6c64b7eeb5