schema tree REFACTOR evaluate features during compilation

So that the compiled schema tree reflects the state
of all the features.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 89702d1..5e7491b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -118,6 +118,7 @@
     src/schema_compile.c
     src/schema_compile_node.c
     src/schema_compile_amend.c
+    src/schema_features.c
     src/tree_schema.c
     src/tree_schema_free.c
     src/tree_schema_helpers.c