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.
Fixed. Nice catch.