Add a man page for curl_global_sslset()

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

docs/libcurl/Makefile.inc

@@ -17,4 +17,4 @@ man_MANS = curl_easy_cleanup.3 curl_easy_getinfo.3 curl_easy_init.3      \
   curl_multi_timeout.3 curl_formget.3 curl_multi_assign.3                \
   curl_easy_pause.3 curl_easy_recv.3 curl_easy_send.3                    \
   curl_multi_socket_action.3 curl_multi_wait.3 libcurl-symbols.3         \
-  libcurl-thread.3 curl_multi_socket_all.3
+  libcurl-thread.3 curl_multi_socket_all.3 curl_global_sslset.3

docs/libcurl/curl_global_sslset.3

@@ -0,0 +1,69 @@
+.\" **************************************************************************
+.\" *                                  _   _ ____  _
+.\" *  Project                     ___| | | |  _ \| |
+.\" *                             / __| | | | |_) | |
+.\" *                            | (__| |_| |  _ <| |___
+.\" *                             \___|\___/|_| \_\_____|
+.\" *
+.\" * 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
+.\" * are also available at https://curl.haxx.se/docs/copyright.html.
+.\" *
+.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+.\" * copies of the Software, and permit persons to whom the Software is
+.\" * furnished to do so, under the terms of the COPYING file.
+.\" *
+.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+.\" * KIND, either express or implied.
+.\" *
+.\" **************************************************************************
+.TH curl_global_sslset 3 "15 July 2017" "libcurl 7.56" "libcurl Manual"
+.SH NAME
+curl_global_sslset - Select SSL backend to use with libcurl
+.SH SYNOPSIS
+.B #include <curl/curl.h>
+.sp
+.BI "CURLsslset curl_global_sslset(curl_sslbackend " id ", const char *" name
+.BI ", curl_ssl_backend ***" avail ");"
+.ad
+.SH DESCRIPTION
+This function configures at runtime which SSL backend to use with libcurl. This
+function can only be called once, and it must be called \fBbefore\fP
+curl_global_init().
+
+The backend can be identified by the id (e.g. CURLSSLBACKEND_OPENSSL). The
+backend can also be specified via the name parameter (passing -1 as id).
+If both id and name are specified, the name will be ignored. If neither id
+nor name are specified, the function will fail with
+CURLSSLSET_UNKNOWN_BACKEND and set the "avail" pointer to the
+NULL-terminated list of available backends.
+
+Upon success, the function returns CURLSSLSET_OK.
+
+If the specified SSL backend is not available, the function returns
+CURLSSLSET_UNKNOWN_BACKEND and sets the "avail" pointer to a NULL-terminated
+list of available SSL backends.
+
+The SSL backend can be set only once. If it has already been set, a
+subsequent attempt to change it will result in a CURLSSLSET_TOO_LATE.
+
+\fBThis function is not thread safe.\fP You must not call it when any other
+thread in the program (i.e. a thread sharing the same memory) is running.
+This doesn't just mean no other thread that is using libcurl.
+
+.SH AVAILABILITY
+This function was added in libcurl 7.56.0. Before this version, there was no
+support for choosing SSL backends at runtime.
+.SH RETURN VALUE
+If this function returns CURLSSLSET_OK, the backend was successfully selected.
+
+If the chosen backend is unknown (or support for the chosed backend has not
+been compiled into libcurl), the function returns CURLSSLSET_UNKNOWN_BACKEND.
+
+If the backend had been configured previously, or if curl_global_init() has
+already been called, the function returns CURLSSLSET_TOO_LATE.
+.SH "SEE ALSO"
+.BR curl_global_init "(3), "
+.BR libcurl "(3) "

docs/libcurl/libcurl.3

@@ -38,6 +38,10 @@ while using libcurl.  This essentially means you call
 \fIcurl_global_cleanup(3)\fP at the end.  See \fBGLOBAL CONSTANTS\fP below for
 details.
 
+If libcurl was compiled with support for multiple SSL backends, the function
+\fIcurl_global_sslset(3)\fP can be called before \fIcurl_global_init(3)\fP
+to select the active SSL backend.
+
 To transfer files, you create an "easy handle" using \fIcurl_easy_init(3)\fP
 for a single individual transfer (in either direction). You then set your
 desired set of options in that handle with \fIcurl_easy_setopt(3)\fP. Options