conlang: Move all cl-libs into the compiler directory

compiler/cl-ast/src/ast_visitor.rs

@@ -0,0 +1,8 @@
+//! Contains an [immutable visitor](Visit) and an [owned folder](Fold) trait,
+//! with default implementations across the entire AST
+
+pub mod fold;
+pub mod visit;
+
+pub use fold::Fold;
+pub use visit::Visit;