AC_SUBST HAVE_LIBZ for curl-config.in

configure.in

@@ -536,7 +536,9 @@ fi
 dnl AC_CHECK_FUNC(gzread, , AC_CHECK_LIB(z, gzread))
 AC_CHECK_LIB(z, gzread, [AM_CONDITIONAL(CONTENT_ENCODING, true) 
 		         AC_DEFINE(HAVE_LIBZ)
-			 LIBS="$LIBS -lz"])
+			 LIBS="$LIBS -lz"
+                         HAVE_LIBZ="1"
+                         AC_SUBST(HAVE_LIBZ)])
 
 dnl Default is to try the thread-safe versions of a few functions
 OPT_THREAD=on

curl-config.in

@@ -66,6 +66,9 @@ while test $# -gt 0; do
 	if test "@IPV6_ENABLED@" = "1"; then
           echo "IPv6"
         fi
+	if test "@HAVE_LIBZ@" = "1"; then
+          echo "libz"
+        fi
 	if test "@CURL_DISABLE_HTTP@" = "1"; then
           echo "HTTP-disabled"
         fi