Consider alloca in special in region

src/analyses/region.ml

@@ -158,7 +158,7 @@ struct
   let special ctx (lval: lval option) (f:varinfo) (arglist:exp list) : D.t =
     let desc = LibraryFunctions.find f in
     match desc.special arglist with
-    | Malloc _ | Calloc _ | Realloc _ -> begin
+    | Malloc _ | Calloc _ | Realloc _ | Alloca _ -> begin
         match ctx.local, lval with
         | `Lifted reg, Some lv ->
           let old_regpart = ctx.global () in