autoconf/check_libustr.m4: detect whether to use the system libustr or the embedded copy
autoconf/check_libustr.m4: detect whether to use the system libustr or the embedded copy

hstern/wdns,hstern/wdns,d4s/wdns,d4s/wdns,hstern/wdns,hstern/wdns,d4s/wdns