Various fixes for NBSD include.

Various fixes for NBSD include.

This patch include various fixes to NBSD includes.

- unistd.h: Avoid different linkages on non-_NETBSD_SOURCE
 compilation;
- stdlib.h: remove devname declaration.
- sys/select.h: Add _MINIX specific flags.
- limits.h: Add SYMLOOP_MAX and SYMLINK_MAX
- time.h: Fix CLOCKS_PER_SEC and remove BSD's timer_t, as it
  confuses minix own specific timers.
- utmp.h: Set Minix-specific paths and use Minix utmp format.
- param.h: Do not set BSD4_4, as this mostly means sa_len in
  struct sock_addr.
- arch/i386/include/param.h: include <machine/vmparam.h> to
  add PAGE_SIZE and related macros, defined round_page() and
  trunc_page() for minix compatibility.

- dirent.h: remove DIRBLKSIZ and fix d_ino/d_fileno.
- sys/dir.h: ADD from existing includes and edit include
  conditions.
- sys/dirent.h: include <minix/dirent.h>, fix d_ino/d_fileno.

- sys/fd_set.h: set default FD_SETSIZE at __MINIX_OPENMAX, as
  the default NetBSD value is too big and cause vfs to return
  an error.
- sys/cdefs.h: Always include <minix/ansi.h>

- minix/paths.h: Add Minix-specific paths.
- minix/dirent.h: ADD, keep only "direct" and "flex"definitions.
- minix/types.h: include <minix/ansi.h>

- sys/Makefile: add sys/dirent.h and statfs.h (forgot!)
- minix/Makefile: add minix/dirent.h

   nbsd_include/minix-port.patch updated accordingly.