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, 65 insertions, 0 deletions

diff --git a/docs/man/nng_msg_realloc.3.adoc b/docs/man/nng_msg_realloc.3.adoc
new file mode 100644
index 00000000..59c2a2da
--- /dev/null
+++ b/docs/man/nng_msg_realloc.3.adoc
@@ -0,0 +1,65 @@
+= nng_msg_realloc(3)
+//
+// 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_msg_realloc - reallocate a message
+
+== SYNOPSIS
+
+[source, c]
+----
+#include <nng/nng.h>
+
+int nng_msg_realloc(nng_msg *msg, size_t size);
+----
+
+== DESCRIPTION
+
+The `nng_msg_realloc()` function re-allocates a message so that it has
+a body of length _size_.
+This message attempts to avoid extra allocations,
+and will reuse the existing memory when possible.
+
+TIP: One way to further reduce message allocations is to allocate a message
+larger than needed, then use this function or
+<<nng_msg_chop.3#,`nng_msg_chop()`>> to reduce the message size
+to that actually needed.
+The extra space left
+over will still be present in the message, so that when the message size
+needs to grow due to this function or <<nng_msg_append.3#,`nng_msg_append()`>>
+no actual memory allocations need to take place.
+
+NOTE: Pointers to message body and header content obtained prior to this
+function must not be in use, as the underlying memory used for the message
+may have changed, particularly if the message size is increasing.
+
+== RETURN VALUES
+
+This function returns 0 on success, and non-zero otherwise.
+
+== ERRORS
+
+`NNG_ENOMEM`:: Insufficient free memory exists to reallocate a message.
+
+== SEE ALSO
+
+<<nng_msg_alloc.3#,nng_msg_alloc(3)>>,
+<<nng_msg_append.3#,nng_msg_append(3)>>,
+<<nng_msg_body.3#,nng_msg_body(3)>>,
+<<nng_msg_chop.3#,nng_msg_chop(3)>>,
+<<nng_msg_free.3#,nng_msg_free(3)>>,
+<<nng_msg_insert.3#,nng_msg_insert(3)>>,
+<<nng_msg_len.3#,nng_msg_len(3)>>,
+<<nng_msg_trim.3#,nng_msg_trim(3)>>,
+<<nng_strerror.3#,nng_strerror(3)>>,
+<<nng_msg.5#,nng_msg(5)>>,
+<<nng.7#,nng(7)>>