fixes arguments attributes in the callsites plugin (#1034)

* fixes arguments attributes in the callsites plugin

When attributes are assigned to a newly created synthetic argument term
in the callsites plugin, we don't take into consideration attributes
from the original argument term. This PR fixes this and now all the
attributes from origin argument term are assigned to the new one.

* a couple cosmetic changes

lib/bap_c/bap_c_attr.ml

@@ -69,5 +69,5 @@ module Gnu = struct
     register_attr "malloc" (set Sub.malloc);
     register_attr "noreturn" (set Sub.noreturn);
     register_attr "returns_twice" (set Sub.returns_twice);
-    register_attr "noreturn" (set Sub.nothrow)
+    register_attr "nothrow" (set Sub.nothrow)
 end

plugins/callsites/callsites_main.ml

@@ -14,9 +14,8 @@ let callee call prog = match Call.target call with
 let require x = Option.some_if x ()
 
 let def_of_arg arg =
-  let x = Arg.lhs arg in
-  let e = Arg.rhs arg in
-  Some (Def.create x e)
+  let d = Def.create (Arg.lhs arg) (Arg.rhs arg) in
+  Some (Term.with_attrs d (Term.attrs arg))
 
 let intent_matches x y = match Arg.intent x with
   | None -> true