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, 3 insertions, 0 deletions

diff --git a/src/options.hpp b/src/options.hpp
index c1e4dda..1288f72 100644
--- a/src/options.hpp
+++ b/src/options.hpp
@@ -95,6 +95,9 @@ namespace xs
         //  Version of wire protocol to use.
         int protocol;
 
+        //  Filter ID to be used with subscriptions and unsubscriptions.
+        int filter_id;
+
         //  If true, session reads all the pending messages from the pipe and
         //  sends them to the network when socket is closed.
         bool delay_on_close;