[PATCH:xbiff 1/2] Use <paths.h> and _PATH_MAILDIR to find mailboxes if present

[Mark Kettenis]

> From: Alan Coopersmith <alan.coopersmith at oracle.com>
> Date: Fri,  7 Jan 2011 17:23:58 -0800
> 
> Use autoconf to check for paths.h on all systems, instead of
> only including it #ifdef CSRG_BASED
> 
> Makes _PATH_MAILDIR the preferred mail directory path on all systems
> if it's defined, falls back to old per-system hardcoded paths if not.
> 
> Signed-off-by: Alan Coopersmith <alan.coopersmith at oracle.com>

Hmm, Linux systems have had paths.h for ages.  And interestingly
enough it defines _PATH_MAILDIR as /var/mail instead of
/var/spool/mail.  Looks like for really old Linux system the latter
was used, but the FHS 2.0 standard changed it to /var/mail in 1997.
So perhaps the

> +# elif defined(__linux__)
> +#  define MAILBOX_DIRECTORY "/var/spool/mail"
> +# else

should just go.  In any case, not a big issue, just some possible
further cleanup, so feel free to ignore that.

Reviewed-by: Mark Kettenis <kettenis at openbsd.org>