update stdpp

opam

@@ -12,5 +12,5 @@ remove: ["sh" "-c" "rm -rf '%{lib}%/coq/user-contrib/iris'"]
 depends: [
   "coq" { >= "8.6.1" & < "8.8~" }
   "coq-mathcomp-ssreflect" { (>= "1.6.1" & < "1.7~") | (= "dev") }
-  "coq-stdpp" { (= "dev.2017-09-24.0") | (= "dev") }
+  "coq-stdpp" { (= "dev.2017-09-29.0") | (= "dev") }
 ]