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, 53 insertions, 0 deletions

diff --git a/docs/man/nng_http_handler_set_data.3http.adoc b/docs/man/nng_http_handler_set_data.3http.adoc
new file mode 100644
index 00000000..318919a9
--- /dev/null
+++ b/docs/man/nng_http_handler_set_data.3http.adoc
@@ -0,0 +1,53 @@
+= nng_http_handler_set_data(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_handler_get_data - set extra data for HTTP handler
+
+== SYNOPSIS
+
+[source, c]
+----
+#include <nng/nng.h>
+#include <nng/supplemental/http/http.h>
+
+void *nng_http_handler_get_data(nng_http_handler *handler, void *data,
+    void (*dtor)(void *));
+----
+
+== DESCRIPTION
+
+The `nng_http_handler_set_data()` function is used to set an additional
+_data_ for the _handler_.
+The stored _data_ can be retrieved later in the handler function using
+<<nng_http_handler_get_data.3http#,`nng_http_handler_get_data()`>>.
+
+Additionally, when the handler is deallocated, if _dtor_ is not `NULL`,
+then it will be called with _data_ as its argument.
+The intended use of
+this function is deallocate any resources associated with _data_.
+
+== RETURN VALUES
+
+This function returns 0 on success, and non-zero otherwise.
+
+== ERRORS
+
+`NNG_ENOMEM`:: Insufficient free memory to perform the operation.
+`NNG_ENOTSUP`:: No support for HTTP in the library.
+
+== SEE ALSO
+
+<<nng_http_handler_alloc.3http#,nng_http_handler_alloc(3http)>>,
+<<nng_http_handler_get_data.3http#,nng_http_server_get_data(3http)>>,
+<<nng_http_server_add_handler.3http#,nng_http_server_add_handler(3http)>>,
+<<nng.7#,nng(7)>>