CURLOPT_POSTFIELDS.3: explain the 100-continue magic better

.\" *                            | (__| |_| |  _ <| |___

.\" *                             \___|\___/|_| \_\_____|

.\" *

.\" * Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.

.\" * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.

.\" *

.\" * This software is licensed as described in the file COPYING, which

.\" * you should have received as part of this distribution. The terms

\fICURLOPT_POSTFIELDS(3)\fP to an empty string, or set \fICURLOPT_POST(3)\fP to

1 and \fICURLOPT_POSTFIELDSIZE(3)\fP to 0.

Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header.

You can disable this header with \fICURLOPT_HTTPHEADER(3)\fP as usual.

Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header,

and libcurl will add that header automatically if the POST is either known to

be larger than 1024 bytes or if the expected size is unknown. You can disable

this header with \fICURLOPT_HTTPHEADER(3)\fP as usual.

To make multipart/formdata posts (aka RFC2388-posts), check out the

\fICURLOPT_HTTPPOST(3)\fP option combined with \fIcurl_formadd(3)\fP.