fixes #143 Protocols and transports should be "configurable"

This makes all the protocols and transports optional.  All
of them except ZeroTier are enabled by default, but you can
now disable them (remove from the build) with cmake options.

The test suite is modified so that tests still run as much
as they can, but skip over things caused by missing functionality
from the library (due to configuration).

Further, the constant definitions and prototypes for functions
that are specific to transports or protocols are moved into
appropriate headers, which should be included directly by
applications wishing to use these.

We have also added and improved documentation -- all of the
transports are documented, and several more man pages for
protocols have been added.  (Req/Rep and Surveyor are still
missing.)

1 files changed, 7 insertions, 3 deletions

diff --git a/src/transport/ipc/ipc.c b/src/transport/ipc/ipc.c
index afe8afa8..c13dbd34 100644
--- a/src/transport/ipc/ipc.c
+++ b/src/transport/ipc/ipc.c
@@ -704,9 +704,7 @@ static nni_tran_ep nni_ipc_ep_ops = {
 	.ep_options = nni_ipc_ep_options,
 };
 
-// This is the IPC transport linkage, and should be the only global
-// symbol in this entire file.
-struct nni_tran nni_ipc_tran = {
+static nni_tran nni_ipc_tran = {
 	.tran_version = NNI_TRANSPORT_VERSION,
 	.tran_scheme  = "ipc",
 	.tran_ep      = &nni_ipc_ep_ops,
@@ -714,3 +712,9 @@ struct nni_tran nni_ipc_tran = {
 	.tran_init    = nni_ipc_tran_init,
 	.tran_fini    = nni_ipc_tran_fini,
 };
+
+int
+nng_ipc_register(void)
+{
+	return (nni_tran_register(&nni_ipc_tran));
+}