check for Exuberant Ctags etags

CHANGES

+ 688.	[func]		"make tags" now works on systems with the
+			"Exuberant Ctags" etags.
 
  687.	[bug]		Only say we have IPv6, with sufficent functionality,
 			if it has actually been tested.  [RT #586]

configure.in

@@ -18,7 +18,7 @@ AC_DIVERT_PUSH(AC_DIVERSION_NOTICE)dnl
 esyscmd([sed "s/^/# /" COPYRIGHT])dnl
 AC_DIVERT_POP()dnl
 
-AC_REVISION($Revision: 1.213 $)
+AC_REVISION($Revision: 1.214 $)
 
 AC_INIT(lib/dns/name.c)
 AC_PREREQ(2.13)
@@ -56,7 +56,23 @@ which ar resides, or set AR in the environment with the full path to ar.
 		;;
 esac
 
+#
+# Etags.
+#
 AC_PATH_PROGS(ETAGS, etags emacs-etags)
+#
+# Some systems, e.g. RH7, have the Exuberant Ctags etags instead of
+# GNU emacs etags, and it requires the -L flag.
+#
+if test "X$ETAGS" != "X"; then
+	AC_MSG_CHECKING(for Exuberant Ctags etags)
+	if $ETAGS --version 2>&1 | grep 'Exuberant Ctags' >/dev/null 2>&1; then
+		AC_MSG_RESULT(yes)
+		ETAGS="$ETAGS -L"
+	else
+		AC_MSG_RESULT(no)
+	fi
+fi
 AC_SUBST(ETAGS)
 
 #