[RFC] Replace vim_strncpy with strlcpy

I also notice a lot of repeat copying from the same buffer to the same buffer:

```
...
2014/06/09 18:50:48 [debug @ xstrlcpy:295] 49234 - ratio: (19/200) 0.095000 (src: 0x7febd621f630, dst: 0x7fff58f1b590)
2014/06/09 18:50:48 [debug @ xstrlcpy:295] 49234 - ratio: (19/200) 0.095000 (src: 0x7febd621f630, dst: 0x7fff58f1b590)
2014/06/09 18:50:48 [debug @ xstrlcpy:295] 49234 - ratio: (19/200) 0.095000 (src: 0x7febd621f630, dst: 0x7fff58f1b590)
...
```