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, 130 insertions, 0 deletions

diff --git a/docs/man/nng_pipe_getopt.3.adoc b/docs/man/nng_pipe_getopt.3.adoc
new file mode 100644
index 00000000..598de053
--- /dev/null
+++ b/docs/man/nng_pipe_getopt.3.adoc
@@ -0,0 +1,130 @@
+= nng_pipe_getopt(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_pipe_getopt - get pipe option
+
+== SYNOPSIS
+
+[source, c]
+-----------
+#include <nng/nng.h>
+
+int nng_pipe_getopt(nng_pipe p, const char *opt, void *val, size_t *valszp);
+
+int nng_pipe_getopt_int(nng_pipe p, const char *opt, int *ivalp);
+
+int nng_pipe_getopt_ms(nng_pipe p, const char *opt, nng_duration *durp);
+
+int nng_pipe_getopt_size(nng_pipe p, const char *opt, size_t *zp);
+
+int nng_pipe_getopt_uint64(nng_pipe p, const char *opt, uint64_t *u64p);
+-----------
+
+== DESCRIPTION
+
+The `nng_pipe_getopt()` functions are used to retrieve option values for
+the <<nng_pipe.5#,pipe>> _p_.
+The actual options that may be retrieved in this way
+vary, and many are documented in <<nng_options.5#,nng_options(5)>>.
+Additionally some transport-specific options are documented with the
+transports themselves, and some protocol-specific options are documented
+with the protocol.
+
+NOTE: All "options" on a pipe are read-only values, and intended to
+facilitate understanding the identity of an associated peer.
+Modification of options must be done on the listener or dialer using either
+<<nng_listener_setopt.3#,`nng_listener_setopt()`>> or
+<<nng_dialer_getopt.3#,`nng_dialer_getopt()`>>
+
+Any option that is set on a dialer or listener will normally be retrievable
+from pipes created by that dialer or listener.
+
+In all of these forms, the option _opt_ is retrieved from the pipe _p_.
+
+The details of the type, size, and semantics of the option will depend
+on the actual option, and will be documented with the option itself.
+
+=== `nng_pipe_getopt()`::
+
+This is untyped, and can be used to retrieve the value of any option.
+A pointer to a buffer to receive the value in _val_, and the size of the
+buffer shall be stored at the location referenced by _valszp_.
+
+When the function returns, the actual size of the data copied (or that
+would have been copied if sufficient space were present) is stored at
+the location referened by _valszp_.
+If the caller's buffer is not large enough to hold the entire object,
+then the copy is truncated.
+Therefore the caller should check for trncation by verifying that the
+size returned in _valszp_ does not exceed the original buffer size.
+
+It is acceptable to pass `NULL` for _val_ if the value in _valszp_ is zero.
+This can be used to determine the size of the buffer needed to receive
+the object.
+
+TIP: Generally, it will be easier to use one of the typed forms instead.
+Note however that no validation that the option is actually of the associated
+type is performed, so the caller must take care to use the *correct* typed form.
+
+=== `nng_pipe_getopt_int()`::
+
+This function is for options which take an integer (`int`) or boolean (`bool`).
+The value will be stored at _ivalp_.  For booleans the value will be eiher 0
+(`false`) or 1 (`true`).
+
+=== `nng_pipe_getopt_ms()`::
+
+This function is used to retrieve time durations
+(<<nng_duration.5#,`nng_duration`) in milliseconds, which are stored in
+_durp_.
+
+=== `nng_pipe_getopt_size()`::
+
+This function is used to retrieve a size into the pointer _zp_,
+typically for buffer sizes, message maximum sizes, and similar options.
+
+=== `nng_pipe_getopt_uint64()`::
+
+This function is used to retriev a 64-bit unsigned value into the value
+referenced by _u64p_.
+This is typically used for options
+related to identifiers, network numbers, and similar.
+
+// XXX: nng_pipe_getopt_ptr is not supported, and would carry some risks,
+// as the pipe may not survive, and the endpoint options may not survive,
+// leading to questions about pointer validity.
+// The last form, `nng_pipe_getopt_ptr()`, is used to retrieve a
+// pointer _ptr_ to structured data.  The data referenced by _ptr_ is
+// generally managed using other functions.
+// Note that this form is somewhat special in that the object is generally
+// not copied, but instead the *pointer* to the object is copied.
+
+== RETURN VALUES
+
+This function returns 0 on success, and non-zero otherwise.
+
+== ERRORS
+
+`NNG_ECLOSED`:: Parameter _p_ does not refer to an open pipe.
+`NNG_ENOTSUP`:: The option _opt_ is not supported.
+`NNG_EWRITEONLY`:: The option _opt_ is write-only.
+
+== SEE ALSO
+
+<<nng_dialer_setopt.3#,nng_dialer_setopt(3)>>
+<<nng_getopt.3#,nng_getopt(3)>>,
+<<nng_listener_setopt.3#,nng_listener_setopt(3)>>
+<<nng_msg_get_pipe.3#,nng_msg_get_pipe(3)>>
+<<nng_strerror.3#,nng_strerror(3)>>,
+<<nng_options.5#,nng_options(5)>>,
+<<nng.7#,nng(7)>>