Bump Iris, fix build.

opam

@@ -11,5 +11,5 @@ build: [make "-j%{jobs}%"]
 install: [make "install"]
 remove: [ "sh" "-c" "rm -rf '%{lib}%/coq/user-contrib/lrust'" ]
 depends: [
-  "coq-iris" { (= "dev.2018-02-20.1") | (= "dev") }
+  "coq-iris" { (= "dev.2018-02-21.1") | (= "dev") }
 ]

theories/lang/lib/memcpy.v

-From iris.base_logic.lib Require Import namespaces.
 From lrust.lang Require Export notation.
 From lrust.lang Require Import heap proofmode.
 Set Default Proof Using "Type".

theories/lang/lib/new_delete.v

-From iris.base_logic.lib Require Import namespaces.
 From lrust.lang Require Export notation.
 From lrust.lang Require Import heap proofmode memcpy.
 Set Default Proof Using "Type".

theories/lang/lib/swap.v

-From iris.base_logic.lib Require Import namespaces.
 From lrust.lang Require Export notation.
 From lrust.lang Require Import heap proofmode.
 Set Default Proof Using "Type".

theories/lang/proofmode.v

-From iris.base_logic Require Import namespaces.
 From iris.program_logic Require Export weakestpre.
 From iris.proofmode Require Import coq_tactics.
 From iris.proofmode Require Export tactics.