fix leaking DNS suffix search list on Windows (#711)

ares__strsplit provides a newly allocated buffer, so suffix list in
line variable isn't referenced anymore. Related ares_free seems to
have gone missing during refactoring made in #594

Fix By: Vojtěch Vobr (@vojtechvobr)

src/lib/ares_sysconfig.c

@@ -624,6 +624,7 @@ static ares_status_t ares__init_sysconfig_windows(ares_sysconfig_t *sysconfig)
 
   if (get_SuffixList_Windows(&line)) {
     sysconfig->domains = ares__strsplit(line, ", ", &sysconfig->ndomains);
+    ares_free(line);
     if (sysconfig->domains == NULL) {
       status = ARES_EFILE;
     }