build: further fixes for broken if_bridge.h

Commit c308a9ae was incomplete; it resolved the configure failure,
but not a later build failure.

* src/util/virnetdevbridge.c: Include pre-req header.
* configure.ac (AC_CHECK_HEADERS): Prefer standard in.h over
non-standard ip6.h.
(cherry picked from commit 1bf661ca)
(cherry picked from commit 2c7638fd)

Conflicts:
	src/util/virnetdevbridge.c

configure.ac

@@ -859,7 +859,7 @@ if test "$with_linux" = "yes"; then
   if test "$with_qemu" = "yes" || test "$with_lxc" = "yes" ; then
     AC_CHECK_HEADERS([linux/param.h linux/sockios.h linux/if_bridge.h linux/if_tun.h],,
       [AC_MSG_ERROR([You must install kernel-headers in order to compile libvirt with QEMU or LXC support])],
-      [[#include <netinet/ip6.h>
+      [[#include <netinet/in.h>
       ]])
   fi
 fi

src/util/virnetdevbridge.c

@@ -30,9 +30,8 @@
 #include "intprops.h"
 
 #include <sys/ioctl.h>
-#ifdef HAVE_NET_IF_H
-# include <net/if.h>
-#endif
+#include <sys/socket.h>
+#include <net/if.h>
 #include <netinet/in.h>
 
 #ifdef __linux__