r308432: Capsicumized `basename` make zsh prompt broken

Hi,
Here is a minimal config of zsh prompt invoking `basename`:
```
└─[iblis_at_abeing]% cat /home/ib-test/.zshenv

function set_prompt {
     prompt="$(basename $HOME) >"
}

function zle-line-init zle-keymap-select {
         set_prompt
         zle reset-prompt
}

zle -N zle-line-init
zle -N zle-keymap-select

set_prompt
```

and launching zsh will get something like this:

```
└─[iblis_at_abeing]% sudo su ib-test

ib-test >basename: capsicum: Bad file descriptor
 >
 >basename: capsicum: Bad file descriptor
 >
```


To be honest, I have no idea about what casper/caspicum is. I just 
changed the `basename.c` and zsh work again.

Index: basename.c
===================================================================
--- basename.c (revision 309213)
+++ basename.c (working copy)
_at__at_ -65,7 +65,7 _at__at_

setlocale(LC_ALL, "");

- if (caph_limit_stdio() < 0 || (cap_enter() < 0 && errno != ENOSYS))
+ if (cap_enter() < 0 && errno != ENOSYS)
err(1, "capsicum");

aflag = 0;


Any idea?

--
Iblis Lin