Prior to this change when no file descriptors were ready on platforms
other than Windows the multi examples would sleep whatever was in
timeout, which may or may not have been less than the minimum
recommended value [1] of 100ms.
[1]: http://curl.haxx.se/libcurl/c/curl_multi_fdset.html
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
Simplified the SMTP multi example as this example should demonstrate
the differences the easy and multi interfaces rather than introduce new
concepts such as user authentication and TLS which are shown in the TLS
and SSL examples.
Replaced the use of CURLOPT_USERPWD for the preferred CURLOPT_USERNAME
and CURLOPT_PASSWORD options and used the same username and password for
all email examples which is the same as that used in the test suite.
All C and H files now (should) feature the proper project curl source
code header, which includes basic info, a copyright statement and some
basic disclaimers.
An example application source code sending SMTP mail with the multi
interface. It is based on the code Alona Rossen provided, which in turn
is based on existing example/test code, and I converted it even more
into a decent example with a fair multi API use, put the info required
to edit at the top and I added some comments.
