MINOR: proxies: Add a per-thread group lbprm struct.

Add a new structure in the per-thread groups proxy structure, that will
contain whatever is per-thread group in lbprm.
It will be accessed as p->per_tgrp[tgid].lbprm.

Author: Olivier Houchard

include/haproxy/backend-t.h

@@ -144,6 +144,11 @@
  */
 #define BE_WEIGHT_SCALE 16
 
+/* LB parameters for all algorithms, with one instance per thread-group */
+struct lbprm_per_tgrp {
+	union {
+	};
+};
 /* LB parameters for all algorithms */
 struct lbprm {
 	union { /* LB parameters depending on the algo type */

include/haproxy/proxy-t.h

@@ -302,6 +302,7 @@ struct error_snapshot {
 /* Each proxy will have one occurrence of this structure per thread group */
 struct proxy_per_tgroup {
 	struct queue queue;
+	struct lbprm_per_tgrp lbprm;
 } THREAD_ALIGNED(64);
 
 struct proxy {