[CLEANUP] Move counters to dedicated structures

Move counters from "struct proxy" and "struct server"
to "struct pxcounters" and "struct svcounters".

This patch should make no functional change.
diff --git a/include/proto/proxy.h b/include/proto/proxy.h
index 0ad1e7f..f293b1b 100644
--- a/include/proto/proxy.h
+++ b/include/proto/proxy.h
@@ -66,9 +66,9 @@
 }
 
 /* increase the number of cumulated connections on the designated frontend */
-static void inline proxy_inc_fe_ctr(struct proxy *fe)
+static void inline proxy_inc_fe_ctr(struct listener *l, struct proxy *fe)
 {
-	fe->cum_feconn++;
+	fe->counters.cum_feconn++;
 	update_freq_ctr(&fe->fe_sess_per_sec, 1);
 	if (fe->fe_sess_per_sec.curr_ctr > fe->fe_sps_max)
 		fe->fe_sps_max = fe->fe_sess_per_sec.curr_ctr;
@@ -77,7 +77,7 @@
 /* increase the number of cumulated connections on the designated backend */
 static void inline proxy_inc_be_ctr(struct proxy *be)
 {
-	be->cum_beconn++;
+	be->counters.cum_beconn++;
 	update_freq_ctr(&be->be_sess_per_sec, 1);
 	if (be->be_sess_per_sec.curr_ctr > be->be_sps_max)
 		be->be_sps_max = be->be_sess_per_sec.curr_ctr;