Need better timeout control in client library

[dank at kegel.com]

We have a Linux box which hangs mysteriously when
the app calls cupsGetDests to get a list of printers.

Turns out the connect to the localhost's CUPS daemon
is hanging in state SYN_SENT because there is
some firewall setting causing SYN packets to be
dropped.  This is not a common situation, but
it does happen once in a while.

It would be nice if the cups client library provided
a way to test the connection to the default
server, e.g.
  cupsStartConnect();
  cupsFinishConnect(bool wait, int timeout_in_seconds);
Then the app could start a nonblocking connect
on startup, and check for connection completion
at its leisure without freezing its UI.

How's that sound?