XS_PLUGIN and XS_FILTER implementation

This patch introduces following features:
- XS_PLUGIN context option to add plugins to libxs
- XS_FILTER option to switch between different filter types
- Automatic loading of plug-ins is *not* implemented.

From the implementation point of view:
- standard prefix filter is implemented as a pluggable filter
- trie_t and mtrie_t are joined into a single class
- the code for 0MQ/3.1 compatibility is left in in the form of comments
- new test for testing re-subscriptions is added
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/wire.hpp b/src/wire.hpp
index 6d1e11b..f840fce 100644
--- a/src/wire.hpp
+++ b/src/wire.hpp
@@ -23,6 +23,10 @@
 
 #include "stdint.hpp"
 
+//  Protocol-related constants.
+#define XS_CMD_SUBSCRIBE 1
+#define XS_CMD_UNSUBSCRIBE 2
+
 namespace xs
 {