[MEDIUM] implement bind-process to limit service presence by process

The "bind-process" keyword lets the admin select which instances may
run on which process (in multi-process mode). It makes it easier to
more evenly distribute the load across multiple processes by avoiding
having too many listen to the same IP:ports.
diff --git a/include/types/proxy.h b/include/types/proxy.h
index cc50690..2f67791 100644
--- a/include/types/proxy.h
+++ b/include/types/proxy.h
@@ -258,6 +258,7 @@
 	int uuid;				/* universally unique proxy ID, used for SNMP */
 	int next_svid;				/* next server-id, used for SNMP */
 	unsigned int backlog;			/* force the frontend's listen backlog */
+	unsigned int bind_proc;			/* bitmask of processes using this proxy. 0 = all. */
 };
 
 struct switching_rule {