fixes #286 nng_pair0_open (and all others) need man page

fixes #279 consider restructuring man sections

This represents a rather significant rework, and major editing
effort, for the entire set of manual pages.

All of the pages now have a section number in their filename;
this assists in some other tooling, particularly ebook generation
as every link needs to be programmatically modified when combined
into an ebook.

Section 5 is introduced, and populated with pages for the main
types, and all options are now documented.

Numerous errors have been corrected, including rewriting certain
portions such as the header section of the surveyor protocol.

Much work has been done to facilitate index generation, although
certainly more work remains here.

Every internal link within these pages now resolves; there are no
more dead links.  (This is required to generate Kindle format books.)

1 files changed, 51 insertions, 0 deletions

diff --git a/docs/man/nng_http_req_del_header.3http.adoc b/docs/man/nng_http_req_del_header.3http.adoc
new file mode 100644
index 00000000..ff3d045f
--- /dev/null
+++ b/docs/man/nng_http_req_del_header.3http.adoc
@@ -0,0 +1,51 @@
+= nng_http_req_set_header(3http)
+//
+// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2018 Capitar IT Group BV <info@capitar.com>
+//
+// This document is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+== NAME
+
+nng_http_req_set_header - set HTTP request header
+
+== SYNOPSIS
+
+[source, c]
+----
+#include <nng/nng.h>
+#include <nng/supplemental/http/http.h>
+
+int nng_http_req_set_header(nng_http_req *req, const char *key);
+----
+
+== DESCRIPTION
+
+The `nng_http_req_del_header()` removes all HTTP headers with the
+associated _key_ from the request structure _req_.
+
+The value of _key_ is case insensitive, and should not include the final
+colon in an HTTP header.
+For example, specifying `Host` or `hOSt` are
+equivalent, whereas the value `Host:` is not a legal header key.
+
+== RETURN VALUES
+
+This function returns 0 on success, and non-zero otherwise.
+
+== ERRORS
+
+`NNG_ENOENT`:: No header with the key _key_ was present.
+`NNG_ENOTSUP`:: No support for HTTP in the library.
+
+== SEE ALSO
+
+<<nng_http_req_alloc.3http#,nng_http_req_alloc(3http)>>,
+<<nng_http_req_add_header.3http#,nng_http_req_add_header(3http)>>,
+<<nng_http_req_del_header.3http#,nng_http_req_del_header(3http)>>,
+<<nng_http_req_get_header.3http#,nng_http_req_get_header(3http)>>,
+<<nng.7#,nng(7)>>