sctp: move to plugins, disabled by default

Removed sctp buffer metadata from vnet/buffer.h, added it to the
plugin. Add registration APIs for plugin-based vlib_buffer_opaque /
opaque2 decoders, used by "pcap dispatch trace ..." for display in the
wireshark dissector.

Type:refactor

Not actively maintained.

Change-Id: Ie4cb6ba66f68b3b3a7d7d2c63c917fdccf994371
Signed-off-by: Florin Coras <fcoras@cisco.com>
Signed-off-by: Dave Barach <dave@barachs.net>

test/test_sctp.py

@@ -11,6 +11,7 @@ class TestSCTP(VppTestCase):
 
     @classmethod
     def setUpClass(cls):
+        cls.extra_vpp_plugin_config.append("plugin sctp_plugin.so { enable }")
         super(TestSCTP, cls).setUpClass()
 
     @classmethod