Patch from Björn Schlögl to enable disable-ness of ipv6.

git-svn-id: svn://svn.h5l.se/heimdal/trunk/heimdal@23428 ec53bebd-3082-4978-b11e-865c3cabbd6b

cf/krb-ipv6.m4

@@ -2,13 +2,17 @@ dnl $Id$
 dnl
 dnl test for IPv6
 dnl
+ac_cv_lib_ipv6=check
+
 AC_DEFUN([AC_KRB_IPV6], [
 AC_ARG_WITH(ipv6,
 	AS_HELP_STRING([--without-ipv6],[do not enable IPv6 support]),[
-if test "$withval" = "no"; then
-	ac_cv_lib_ipv6=no
-fi])
+        ac_cv_lib_ipv6="$withval"
+])
 save_CFLAGS="${CFLAGS}"
+
+if test "X$ac_cv_lib_ipv6" != "Xno"; then
+
 	AC_CACHE_CHECK([for IPv6 stack type], rk_cv_v6type, 
 	[dnl check for different v6 implementations (by itojun)
 	v6type=unknown
@@ -85,8 +89,7 @@ if test "$v6lib" != "none"; then
 				break
 			fi
 		done
-fi
-])
+	fi])
 
 	AC_CACHE_CHECK([for IPv6], rk_cv_lib_ipv6, [
 	AC_LINK_IFELSE([AC_LANG_PROGRAM([[
@@ -116,6 +119,8 @@ AC_LINK_IFELSE([AC_LANG_PROGRAM([[
 ]])],
 	[ac_cv_lib_ipv6=yes],
 	[ac_cv_lib_ipv6=no])])
+fi
+
 if test "$ac_cv_lib_ipv6" = yes; then
   AC_DEFINE(HAVE_IPV6, 1, [Define if you have IPv6.])
 else