Rename rustc_mir to rustc_const_eval.

compiler/rustc_const_eval/src/util/mod.rs

@@ -0,0 +1,8 @@
+pub mod aggregate;
+mod alignment;
+pub mod collect_writes;
+mod find_self_call;
+
+pub use self::aggregate::expand_aggregate;
+pub use self::alignment::is_disaligned;
+pub use self::find_self_call::find_self_call;