Add a dominator tree implementation.

cranelift/src/libcretonne/lib.rs

@@ -10,7 +10,7 @@ pub const VERSION: &'static str = env!("CARGO_PKG_VERSION");
 pub mod ir;
 pub mod write;
 pub mod cfg;
-
+pub mod dominator_tree;
 pub mod entity_map;
 
 #[cfg(test)]pub mod test_utils;