slirp: Add domainname option to slirp's DHCP server

This patch will allow the user to include the domainname option in
replies from the built-in DHCP server.

Signed-off-by: Benjamin Drung <benjamin.drung@profitbricks.com>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
diff --git a/slirp/slirp.h b/slirp/slirp.h
index 06febfc..10b4108 100644
--- a/slirp/slirp.h
+++ b/slirp/slirp.h
@@ -193,6 +193,7 @@
     char *bootp_filename;
     size_t vdnssearch_len;
     uint8_t *vdnssearch;
+    char *vdomainname;
 
     /* tcp states */
     struct socket tcb;