Move ICH to rustc_query_system.

compiler/rustc_query_system/src/lib.rs

@@ -1,3 +1,4 @@
+#![feature(assert_matches)]
 #![feature(bool_to_option)]
 #![feature(core_intrinsics)]
 #![feature(hash_raw_entry)]
@@ -14,4 +15,5 @@ extern crate rustc_macros;
 
 pub mod cache;
 pub mod dep_graph;
+pub mod ich;
 pub mod query;