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, 69 insertions, 0 deletions

diff --git a/docs/man/nng_aio.5.adoc b/docs/man/nng_aio.5.adoc
new file mode 100644
index 00000000..4353652d
--- /dev/null
+++ b/docs/man/nng_aio.5.adoc
@@ -0,0 +1,69 @@
+= nng_aio(5)
+//
+// 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_aio - asynchronous I/O handle
+
+== SYNOPSIS
+
+[source, c]
+----
+#include <nng/nng.h>
+
+typedef struct nng_aio nng_aio;
+----
+
+== DESCRIPTION
+
+An `nng_aio`(((aio))) is an opaque structure used in conjuction with
+((asynchronous I/O)) operations.
+Every asynchronous operation uses one of these structures, each of which
+can only be used with a single operation at a time.
+
+Asynchronous operations are performed without blocking calling application
+threads.
+Instead the application registers a "`callback`" function to be executed
+when the operation is complete (whether successfully or not).
+This callback will be executed exactly once.
+
+The asynchronous I/O framework in _nng_ also supports cancellation of
+operations that are already in progress
+(see <<nng_aio_cancel.3#,`nng_aio_cancel()`>>), as well setting a maximum
+timeout for them to complete within
+(see <<nng_aio_set_timeout.3#,`nng_aio_set_timeout()`>>).
+
+It is also possible to initiate an asynchronous operation, and wait for it to
+complete using <<nng_aio_wait.3#,`nng_aio_wait()`>>.
+
+These structures are created using the <<nng_aio_alloc.3#,`nng_aio_alloc()`>>,
+and destroyed using <<nng_aio_free.3#,`nng_aio_free()`>>.
+
+== SEE ALSO
+
+<<nng_aio_abort.3#,nng_aio_abort(3)>>,
+<<nng_aio_alloc.3#,nng_aio_alloc(3)>>,
+<<nng_aio_cancel.3#,nng_aio_cancel(3)>>,
+<<nng_aio_count.3#,nng_aio_count(3)>>,
+<<nng_aio_free.3#,nng_aio_free(3)>>,
+<<nng_aio_get_input.3#,nng_aio_get_input(3)>>,
+<<nng_aio_get_msg.3#,nng_aio_get_msg(3)>>,
+<<nng_aio_get_output.3#,nng_aio_get_output(3)>>,
+<<nng_aio_result.3#,nng_aio_result(3)>>,
+<<nng_aio_set_input.3#,nng_aio_set_input(3)>>,
+<<nng_aio_set_iov.3#,nng_aio_set_iov(3)>>,
+<<nng_aio_set_msg.3#,nng_aio_set_msg(3)>>,
+<<nng_aio_set_timeout.3#,nng_aio_set_timeout(3)>>,
+<<nng_aio_stop.3#,nng_aio_stop(3)>>,
+<<nng_aio_wait.3#,nng_aio_wait(3)>>,
+<<nng_strerror.3#,nng_strerror(3)>>,
+<<nng_aio.5#,nng_aio(5)>>,
+<<nng.7#,nng(7)>>