do not include <libutil.h> needlessly or if it doesn't exist

<libutil.h> and <util.h> on *BSD (some have one, some another)
were #included just for openpty() declaration.  The only file
where this function is actually used is qemu-char.c.

In vl.c and net/tap-bsd.c, none of functions declared in libutil.h
(login logout logwtmp timdomain openpty forkpty uu_lock realhostname
fparseln and a few others depending on version) are used.

Initially the code which is currently in qemu-char.c was in vl.c,
it has been removed into separate file in commit 0e82f34d07
Fri Oct 31 18:44:40 2008, but the #includes were left in vl.c.
So with vl.c, we just remove includes - libutil.h, util.h and
pty.h (which declares only openpty() and forkpty()) from there.

The code in net/tap-bsd.c, which come from net/tap.c, had this

commit 5281d757ef
Author: Mark McLoughlin <markmc@redhat.com>
Date:   Thu Oct 22 17:49:07 2009 +0100

    net: split all the tap code out into net/tap.c

Note this commit not only moved stuff out of net.c to net/tap.c,
but also rewrote large portions of the tap code, and added these
completely unnecessary #includes -- as usual, I question why such
a misleading commit messages are allowed.

Again, no functions defined in libutil.h or util.h on *BSD are
used by neither net/tap.c nor net/tap-bsd.c.  Removing them.

And finally, the only real user for these #includes, qemu-char.c,
which actually uses openpty().  There, the #ifdef logic is wrong.
A GLIBC-based system has <pty.h>, even if it is a variant of *BSD.
So __GLIBC__ should be checked first, and instead of trying to
include <libutil.h> or <util.h>, we include <pty.h>.  If it is not
GLIBC-based, we check for variations between <*util.h> as before.

This patch fixes build of qemu 1.1 on Debian/kFreebsd (well, one
of the two problems): it is a distribution with a FreeBSD kernel,
so it #defines at least __FreeBSD_kernel__, but since it is based
on GLIBC, it has <pty.h>, but current version does not have neither
<util.h> nor <libutil.h>, which the code tries to include 3 times
but uses only once.

Signed-off-By: Michael Tokarev <mjt@tls.msk.ru>
Cc: Aurelien Jarno <aurelien@aurel32.net>

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

net/tap-bsd.c

@@ -33,12 +33,6 @@
 #include <net/if_tap.h>
 #endif
 
-#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__DragonFly__)
-#include <libutil.h>
-#else
-#include <util.h>
-#endif
-
 int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required)
 {
     int fd;

qemu-char.c

@@ -56,20 +56,20 @@
 #include <sys/select.h>
 #ifdef CONFIG_BSD
 #include <sys/stat.h>
-#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
-#include <libutil.h>
-#include <dev/ppbus/ppi.h>
-#include <dev/ppbus/ppbconf.h>
 #if defined(__GLIBC__)
 #include <pty.h>
-#endif
-#elif defined(__DragonFly__)
+#elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__DragonFly__)
 #include <libutil.h>
-#include <dev/misc/ppi/ppi.h>
-#include <bus/ppbus/ppbconf.h>
 #else
 #include <util.h>
 #endif
+#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
+#include <dev/ppbus/ppi.h>
+#include <dev/ppbus/ppbconf.h>
+#elif defined(__DragonFly__)
+#include <dev/misc/ppi/ppi.h>
+#include <bus/ppbus/ppbconf.h>
+#endif
 #else
 #ifdef __linux__
 #include <pty.h>

vl.c

@@ -51,14 +51,12 @@
 #ifdef CONFIG_BSD
 #include <sys/stat.h>
 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__DragonFly__)
-#include <libutil.h>
 #include <sys/sysctl.h>
 #else
 #include <util.h>
 #endif
 #else
 #ifdef __linux__
-#include <pty.h>
 #include <malloc.h>
 
 #include <linux/ppdev.h>
@@ -81,10 +79,6 @@
 #endif
 #endif
 
-#if defined(__OpenBSD__)
-#include <util.h>
-#endif
-
 #if defined(CONFIG_VDE)
 #include <libvdeplug.h>
 #endif