add c-cube's recursive function theory

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/ast/CMakeLists.txt

@@ -36,6 +36,7 @@ z3_add_component(ast
     occurs.cpp
     pb_decl_plugin.cpp
     pp.cpp
+    recfun_decl_plugin.cpp
     reg_decl_plugins.cpp
     seq_decl_plugin.cpp
     shared_occs.cpp