MINOR: spoe: Add counters to log info about SPOE agents

In addition to metrics about time spent in the SPOE, following counters have
been added:

  * applets : number of SPOE applets.
  * idles : number of idle applets.
  * nb_sending : number of streams waiting to send data.
  * nb_waiting : number of streams waiting for a ack.
  * nb_processed : number of events/groups processed by the SPOE (from the
                   stream point of view).
  * nb_errors : number of errors during the processing (from the stream point of
                view).

Log messages has been updated to report these counters. Following pattern has
been added at the end of the log message:

    ... <idles>/<applets> <nb_sending>/<nb_waiting> <nb_error>/<nb_processed>
diff --git a/include/types/spoe.h b/include/types/spoe.h
index b7d54f3..c01a03e 100644
--- a/include/types/spoe.h
+++ b/include/types/spoe.h
@@ -282,6 +282,14 @@
 		__decl_hathreads(HA_SPINLOCK_T lock);
 	} *rt;
 
+	struct {
+		unsigned int applets;            /* # of SPOE applets */
+		unsigned int idles;              /* # of idle applets */
+		unsigned int nb_sending;         /* # of streams waiting to send data */
+		unsigned int nb_waiting;         /* # of streams waiting for a ack */
+		unsigned long long nb_processed; /* # of frames processed by the SPOE */
+		unsigned long long nb_errors;    /* # of errors during the processing */
+	} counters;
 };
 
 /* SPOE filter configuration */