This file was used previously to force C++ linkage.
It's no longer required because most of the code is C++ anyway.

This reverts commit f56c6a18.  This
fix is not necessary anymore because clients are now being deleted by
the timer callback.

Don't use a global loop over the whole client list.

Fixes assertion failure (regression).

Allow creating a closed SocketMonitor instance.

Use WinSock errors on Windows.