Make it clearer that the CURLOPT_PROGRESSFUNCTION callback will be
called more frequently than once per second when things are happening.

Update the documentation on how to specify a HTTP header with no
content.

Also added a (correctly-escaped) backslash to the autoexec.bat
example file and a new Windows character device name with
a colon as examples of other characters that are special
and potentially dangerous (this reverts and reworks commit
7d8d2a54).

If the multi handle's pending timeout is less than what is passed into
this function, it will now opt to use the shorter time anyway since it
is a very good hint that the handle wants to process something in a
shorter time than what otherwise would happen.

curl_multi_wait.3 was updated accordingly to clarify

This is the reason for bug #1224

Bug: http://curl.haxx.se/bug/view.cgi?id=1224
Reported-by: Andrii Moiseiev

A single backslash in the content is not legal nroff syntax.

Reported and fixed by: Eric S. Raymond
Bug: http://curl.haxx.se/bug/view.cgi?id=1234

Reported and fixed by: Eric S. Raymond
Bug: http://curl.haxx.se/bug/view.cgi?id=1233

Bug: http://curl.haxx.se/bug/view.cgi?id=1169

Explain the callback and its arguments better and with more descriptive
text.

Add an XML stream parsing example using Expat. Add missing ignore for
the binary from an unrelated example.

Users using the Secure Transport (darwinssl) back-end can now use a
certificate and private key to authenticate with a site using TLS. Because
Apple's security system is based around the keychain and does not have any
non-public function to create a SecIdentityRef data structure from data
loaded outside of the Keychain, the certificate and private key have to be
loaded into the Keychain first (using the certtool command line tool or
the Security framework's C API) before we can find it and use it.

Documented the the option in curl_easy_setopt() and added it to
symbols-in-versions.

...when mentioning login options. Additional minor clarification of
"Windows builds" to be "Windows builds with SSPI"as a way of enabling
NTLM as Windows builds may be built with OpenSSL to enable NTLM or
without NTLM support altogether.

Thanks to archive.org's wayback machine I updated this document with
some facts from the early httpget/urlget web page:

http://web.archive.org/web/19980216125115/http://www.inf.ufrgs.br/~sagula/urlget.html

Relies on CURLOPT_SSL_CTX_FUNCTION, which is OpenSSL specific

Commit c3ea3eb6 introduced some minor cosmetic errors in
curl_mutli_socket_action(3).

Also note the prohibition on sharing handles across threads.

Update sharing interface documentation to provide exhaustive list of
what it does and does not share.