Use Ptrofs.repr instead of Int.repr for Init_addrof. (#51)

This should fix issue 216 and also allows it to print 64 bit offsets.

exportclight/ExportClight.ml

@@ -109,6 +109,12 @@ let coqint p n =
   then fprintf p "(Int.repr %ld)" n
   else fprintf p "(Int.repr (%ld))" n
 
+let coqptrofs p n =
+  let s = Z.to_string n in
+  if Z.ge n Z.zero
+  then fprintf p "(Ptrofs.repr %s)" s
+  else fprintf p "(Ptrofs.repr (%s))" s
+
 let coqint64 p n =
   let n = camlint64_of_coqint n in
   if n >= 0L
@@ -393,7 +399,7 @@ let init_data p = function
   | Init_float32 n -> fprintf p "Init_float32 %a" coqsingle n
   | Init_float64 n -> fprintf p "Init_float64 %a" coqfloat n
   | Init_space n -> fprintf p "Init_space %ld" (Z.to_int32 n)
-  | Init_addrof(id,ofs) -> fprintf p "Init_addrof %a %a" ident id coqint ofs
+  | Init_addrof(id,ofs) -> fprintf p "Init_addrof %a %a" ident id coqptrofs ofs
 
 let print_variable p (id, v) =
   fprintf p "Definition v_%s := {|@ " (extern_atom id);