Hook the rename() and renameat() syscalls.

Hello, I've hooked the `rename()` and `renameat()` syscalls. Here is an example chisel:

```lua
    f_evt_arg_oldpath = chisel.request_field("evt.arg.oldpath");
    f_evt_arg_newpath = chisel.request_field("evt.arg.newpath");
    if "rename" == evt.field(f_evt_type) and "<" == evt.field(f_evt_dir) then
        print(json.encode({type="<rename", res=tonumber(evt.field(f_evt_arg_res))}));
    end 
    if "rename" == evt.field(f_evt_type) and ">" == evt.field(f_evt_dir) then
        print(json.encode({type=">rename", oldpath=evt.field(f_evt_arg_oldpath),
                           newpath=evt.field(f_evt_arg_newpath), cwd=evt.field(f_proc_cwd)}));
    end 
```

In `parse_rename_renameat_exit()`, I attempted to compute `fulloldpath` and `fullnewpath` but then I didn't know where to put the computed result (so it goes nowhere!).

Willing to do extra work if needed to clean up patch. Thanks for your time reviewing it.