tool: Use Kerberos for supported features
tool: Removed krb4 from the supported features

Although libcurl would never return CURL_VERSION_KERBEROS4 after 7.33,
so would not be output with --version, removed krb4 from the supported
features output.
sasl: Corrected Curl_sasl_build_spn() function description

There was a mismatch in function parameter names.
http2: Don't send Upgrade headers when we already do HTTP/2
examples: Don't call select() to sleep on windows

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