Fix httpd compilation on the FreeBSD

FreeBSD is not exporting s6_addr32 by default, but has it.

Signed-off-by: Alex Samorukov <samm@os2.kiev.ua>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/httpd.c b/networking/httpd.c
index 4c014bc..3cad289 100644
--- a/networking/httpd.c
+++ b/networking/httpd.c
@@ -298,6 +298,11 @@
 # include <sys/sendfile.h>
 #endif
 
+/* see sys/netinet6/in6.h */
+#if defined(__FreeBSD__)
+# define s6_addr32 __u6_addr.__u6_addr32
+#endif
+
 #define DEBUG 0
 
 #define IOBUF_SIZE 8192