Add non_modrs_mods feature gate back in

This allows building with the 1.30 stable compiler

Author: Mark-Simulacrum

chalk-engine/src/lib.rs

@@ -51,6 +51,7 @@
 
 #![feature(in_band_lifetimes)]
 #![feature(step_trait)]
+#![feature(non_modrs_mods)]
 
 #[macro_use]
 extern crate chalk_macros;

chalk-ir/src/lib.rs

@@ -1,5 +1,6 @@
 #![feature(crate_visibility_modifier)]
 #![feature(specialization)]
+#![feature(non_modrs_mods)]
 
 use cast::Cast;
 use chalk_engine::fallible::*;

chalk-solve/src/lib.rs

@@ -1,4 +1,5 @@
 #![feature(crate_visibility_modifier)]
+#![feature(non_modrs_mods)]
 
 #[macro_use]
 extern crate chalk_macros;

src/lib.rs

@@ -6,6 +6,7 @@
 #![feature(specialization)]
 #![feature(step_trait)]
 #![feature(underscore_imports)]
+#![feature(non_modrs_mods)]
 
 extern crate chalk_parse;
 #[macro_use]