Fix nightly build breakage

GabrielMajeri · gnzlbg · commit 20dc1149615e · 2018-10-07T18:54:35.000+02:00
diff --git a/crates/coresimd/src/lib.rs b/crates/coresimd/src/lib.rs
@@ -17,7 +17,7 @@
     repr_simd,
     simd_ffi,
     asm,
-    proc_macro_gen,
+    proc_macro_hygiene,
     integer_atomics,
     stmt_expr_attributes,
     core_intrinsics,
