Fix for the FEATURE_UTMP on the FreeBSD

FreeBSD is not using <utmp.h> and does not define _PATH_UTMPX.
Tested with busybox applets depending on FEATURE_UTMP (e.g. who, users, etc)

Signed-off-by: Alex Samorukov <samm@os2.kiev.ua>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/libbb.h b/include/libbb.h
index dad6fc6..cb63364 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -106,7 +106,11 @@
 #  define updwtmpx updwtmp
 #  define _PATH_UTMPX _PATH_UTMP
 # else
-#  include <utmp.h>
+#  if !defined(__FreeBSD__)
+#   include <utmp.h>
+#  else
+#   define _PATH_UTMPX "/var/run/utx.active"
+#  endif
 #  include <utmpx.h>
 #  if defined _PATH_UTMP && !defined _PATH_UTMPX
 #   define _PATH_UTMPX _PATH_UTMP