Turn some alloca_no_lifetime() calls into plain alloca() calls

The issues that the comments referred to were fixed before the PR even
landed but we never got around to remove the hack of skipping the
lifetime start.

src/librustc_trans/trans/expr.rs

@@ -247,8 +247,7 @@ pub fn trans<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
             immediate_rvalue(load_ty(bcx, global, const_ty), const_ty)
         } else {
             let llty = type_of::type_of(bcx.ccx(), const_ty);
-            // HACK(eddyb) get around issues with lifetime intrinsics.
-            let scratch = alloca_no_lifetime(bcx, llty, "const");
+            let scratch = alloca(bcx, llty, "const");
             let lldest = if !const_ty.is_structural() {
                 // Cast pointer to slot, because constants have different types.
                 PointerCast(bcx, scratch, val_ty(global))
@@ -412,8 +411,7 @@ fn apply_adjustments<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
                 let target = bcx.monomorphize(&target);
                 let llty = type_of::type_of(bcx.ccx(), target);
 
-                // HACK(eddyb) get around issues with lifetime intrinsics.
-                let scratch = alloca_no_lifetime(bcx, llty, "__coerce_target");
+                let scratch = alloca(bcx, llty, "__coerce_target");
                 let target_datum = Datum::new(scratch, target,
                                               Rvalue::new(ByRef));
                 bcx = coerce_unsized(bcx, expr.span, source_datum, target_datum);