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, 70 insertions, 0 deletions

diff --git a/docs/man/nng_sockaddr_in.5.adoc b/docs/man/nng_sockaddr_in.5.adoc
new file mode 100644
index 00000000..94fa18be
--- /dev/null
+++ b/docs/man/nng_sockaddr_in.5.adoc
@@ -0,0 +1,70 @@
+= nng_sockaddr_in(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_sockaddr_in - IPv4 socket address
+
+== SYNOPSIS
+
+[source, c]
+----
+#include <nng/nng.h>
+
+enum sockaddr_family {
+    NNG_AF_INET = 3,
+};
+
+typedef struct {
+    uint16_t sa_family;
+    uint16_t sa_port;
+    uint32_t sa_addr;
+} nng_sockaddr_in;
+----
+
+== DESCRIPTION
+
+(((socket, address, IPv4)))
+An `nng_sockaddr_in` is the flavor of <<nng_sockaddr.5#,`nng_sockaddr`>>
+used to represent TCP (and sometimes UDP) addresses,
+including the Internet Protocol (IP) address and port number.(((port number, TCP)))
+
+This structure is used with IPv4 addresses.
+A different structure, <<nng_sockaddr_in6.5#,`nng_sockaddr_in6`>>, is used
+for IPv6 addresses.
+
+The following structure members are present:
+
+`sa_family`::
+    This field will always have the value ((`NNG_AF_INET`)).
+
+`sa_port`::
+    This field holds the TCP or UDP port number, in network byte-order.
+    A zero value here is used when no specific port number is indicated.
+
+`sa_addr`::
+    This field holds the ((IP addresss))(((address, IPv4))) in
+    network-byte order.
+
+TIP: The `sa_port` and `sa_addr` fields are in network-byte order to
+facilitate their use with system APIs such as `inet_ntop()`.
+Most platforms use some form of BSD-derived network API, which uses
+network-byte order in the various structurs (such as `sockaddr_in`).
+
+IMPORTANT: This field appears similar to BSD `sockaddr_in`, but it is
+_not_ the same, and they may not be used interchangeabley.
+
+== SEE ALSO
+
+<<nng_sockaddr.5#,nng_sockaddr(5)>>,
+<<nng_sockaddr_in6.5#,nng_sockaddr_in6(5)>>,
+<<nng_tcp.7#,nng_tcp(7)>>,
+<<nng.7#,nng(7)>>