Add documentation for supplemental functions.

This includes platform portability stuff like mutexes and threads,
etc.  While here we fixed a problem with nng_opts_parse and we
addressed the type of the platform API.

1 files changed, 56 insertions, 0 deletions

diff --git a/docs/man/nng_mtx_alloc.3supp.adoc b/docs/man/nng_mtx_alloc.3supp.adoc
new file mode 100644
index 00000000..ba4e0c06
--- /dev/null
+++ b/docs/man/nng_mtx_alloc.3supp.adoc
@@ -0,0 +1,56 @@
+= nng_mtx_alloc(3supp)
+//
+// 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_mtx_alloc - allocate mutex
+
+== SYNOPSIS
+
+[source, c]
+----
+#include <nng/nng.h>
+#include <nng/supplemental/util/platform.h>
+
+typedef struct nng_mtx nng_mtx;
+
+int nng_mtx_alloc(nng_mtx **mtxp);
+----
+
+== DESCRIPTION
+
+The `nng_mtx_alloc()` function allocates mutex and returns it in _mtxp_.
+
+The mutex objects created by this function are suitable only for
+simple lock and unlock operations, and are not recursive.
+Every effort has been made to use light-weight underlying primitives when available.
+
+Mutex (mutual exclusion) objects can be thought of as binary semaphores,
+where only a single thread of execution is permitted to "`own`" the semaphore.
+
+Furthermore, a mutex can only be unlocked by the thread that locked it.
+
+== RETURN VALUES
+
+This function returns 0 on success, and non-zero otherwise.
+
+== ERRORS
+
+`NNG_ENOMEM`:: Insufficient free memory exists.
+
+== SEE ALSO
+
+<<nng_cv_alloc.3supp#,nng_cv_alloc(3supp)>>,
+<<nng_mtx_free.3supp#,nng_mtx_free(3supp)>>,
+<<nng_mtx_lock.3supp#,nng_mtx_lock(3supp)>>,
+<<nng_mtx_unlock.3supp#,nng_mtx_unlock(3supp)>>,
+<<nng_strerror.3#,nng_strerror(3)>>,
+<<nng.7#,nng(7)>>