Attribute errors

meck_code_gen:to_forms fails when deprecated attribute is used in a module. 

```erlang
undefined
*unexpected termination of test process*
::{compile_forms,{error,[{[],
                          [{64,erl_lint,
                            {bad_deprecated,{safe_multi_server_call,...}}},
                           {64,erl_lint,{bad_deprecated,{...}}}]}],
                        [{[],[{64,erl_lint,{undefined_behaviour,[...]}}]}]}}
```

This code generates the above error :

```erlang
{attribute,52,module,rpc},
   {attribute,64,behaviour,[gen_server]},
   {attribute,64,deprecated,
              [{safe_multi_server_call,2},{safe_multi_server_call,3}]}
```

If we ignore deprecated the problem is fixed.