Make KCM the default ccache on OS X

If we do not find a default ccache value from krb5-config and we
detect that the host platform is OS X 10.7 or higher, use KCM: as the
default ccache name instead of FILE:/tmp/krb5cc_%{uid}.

ticket: 7964

src/configure.in

@@ -1317,8 +1317,22 @@ if test "x$with_krb5_config" != xno; then
 		: "${DEFCKTNAME=`$with_krb5_config --defcktname`}"
 	fi
 fi
+dnl The outer brackets around the case statement prevent m4 from eating the
+dnl brackets in the glob patterns.
 if test "${DEFCCNAME+set}" != set; then
-	DEFCCNAME=FILE:/tmp/krb5cc_%{uid}
+	[case $host in
+	*-*-darwin[0-9].* | *-*-darwin10.*)
+		# Use the normal default for OS X 10.6 (Darwin 10) and prior.
+		;;
+	*-*-darwin*)
+		# For OS X 10.7 (Darwin 11) and later, the native ccache uses
+		# the KCM daemon.
+		DEFCCNAME=KCM:
+		;;
+	esac]
+	if test "${DEFCCNAME+set}" != set; then
+		DEFCCNAME=FILE:/tmp/krb5cc_%{uid}
+	fi
 fi
 if test "${DEFKTNAME+set}" != set; then
 	DEFKTNAME=FILE:/etc/krb5.keytab