fixes #457 Create stub headers for compatibility

I actually made these real headers, not stubs
While here I made some improvements to the nng_compat man page,
to improve the language and also the presentation on some devices.
(We were going nuts with the icons, instead, I've made a single new
section, called Caveats, that lists a bunch of them.)

This should not have any impact on binary compatibility.

1 files changed, 35 insertions, 0 deletions

diff --git a/src/compat/nanomsg/reqrep.h b/src/compat/nanomsg/reqrep.h
new file mode 100644
index 00000000..9490a8f1
--- /dev/null
+++ b/src/compat/nanomsg/reqrep.h
@@ -0,0 +1,35 @@
+//
+// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2018 Capitar IT Group BV <info@capitar.com>
+//
+// This software 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.
+//
+
+#ifndef NNG_COMPAT_REQREP_H
+#define NNG_COMPAT_REQREP_H
+
+// This header contains interfaces that are intended to offer compatibility
+// with nanomsg v1.0.  These are not the "preferred" interfaces for nng,
+// and consumers should only use these if they are porting software that
+// previously used nanomsg.  New programs should use the nng native APIs.
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// REQ and REP sockopt level.
+#define NN_PROTO_REQREP 3
+#define NN_REQ (NN_PROTO_REQREP * 16 + 0)
+#define NN_REP (NN_PROTO_REQREP * 16 + 1)
+
+// REQ options.  (REP has none.)
+#define NN_REQ_RESEND_IVL (NN_REQ * 16 + 1)
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // NNG_COMPAT_REQREP_H