Insure active_clients is initialized before cleanup() can be called.

Fix reported and observed crash in cleanup() (in ftp, mail, websrvr)
when failing to create the temp directory. This was due to cleanup()
being called before the protected integer "active_clients" was
initialized.

Also, md() needs to return the errno value (not a BOOL) since the
caller may be in another DLL with a different errno (which likely
has a value of 0/no error).