Windows does not support using select() for sleeping without a dummy
socket. Instead use Windows' Sleep() and sleep for 100ms which is the
minimum suggested value in the curl_multi_fdset() doc.
Prior to this change the multi examples would exit prematurely since
select() would error instead of sleeping when called without an fd.
Reported-by: Johan Lantz
Bug: http://curl.haxx.se/mail/lib-2014-11/0221.html
